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	$17.91	8.779%	$19.4823	$19.48	$19.50	$19.50
Purchase #2	$32.45	13.626%	$36.8716	$36.87	$36.85	$36.90
Purchase #3	$20.82	9.140%	$22.7229	$22.72	$22.70	$22.70
Purchase #4	$106.55	7.775%	$114.8343	$114.83	$114.85	$114.80
Purchase #5	$37.57	5.768%	$39.737	$39.74	$39.75	$39.70
Purchase #6	$222.36	3.159%	$229.3844	$229.38	$229.40	$229.40
Purchase #7	$68.44	5.590%	$72.2658	$72.27	$72.25	$72.30
7 purchase totals =	$506.10		$535.2983	$535.29	$535.30	$535.30