Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$219.37	4.401%	$229.0245	$229.02	$229.00	$229.00
Purchase #2	$245.33	8.778%	$266.8651	$266.87	$266.85	$266.90
Purchase #3	$211.90	12.489%	$238.3642	$238.36	$238.35	$238.40
Purchase #4	$128.33	8.736%	$139.5409	$139.54	$139.55	$139.50
Purchase #5	$233.88	13.801%	$266.1578	$266.16	$266.15	$266.20
Purchase #6	$105.50	12.520%	$118.7086	$118.71	$118.70	$118.70
Purchase #7	$230.59	13.323%	$261.3115	$261.31	$261.30	$261.30
7 purchase totals =	$1,374.90		$1,519.9726	$1,519.97	$1,519.90	$1,520.00