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	$40.33	9.763%	$44.2674	$44.27	$44.25	$44.30
Purchase #2	$239.55	10.356%	$264.3578	$264.36	$264.35	$264.40
Purchase #3	$79.60	12.744%	$89.7442	$89.74	$89.75	$89.70
Purchase #4	$93.46	8.340%	$101.2546	$101.25	$101.25	$101.30
Purchase #5	$208.28	4.297%	$217.2298	$217.23	$217.25	$217.20
Purchase #6	$225.33	3.425%	$233.0476	$233.05	$233.05	$233.00
Purchase #7	$109.82	12.860%	$123.9429	$123.94	$123.95	$123.90
7 purchase totals =	$996.37		$1,073.8443	$1,073.84	$1,073.85	$1,073.80