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	$45.92	13.352%	$52.0512	$52.05	$52.05	$52.10
Purchase #2	$142.52	6.829%	$152.2527	$152.25	$152.25	$152.30
Purchase #3	$235.64	12.468%	$265.0196	$265.02	$265.00	$265.00
Purchase #4	$90.94	4.145%	$94.7095	$94.71	$94.70	$94.70
Purchase #5	$196.77	5.267%	$207.1339	$207.13	$207.15	$207.10
Purchase #6	$160.40	12.402%	$180.2928	$180.29	$180.30	$180.30
Purchase #7	$84.48	5.486%	$89.1146	$89.11	$89.10	$89.10
7 purchase totals =	$956.67		$1,040.5743	$1,040.56	$1,040.55	$1,040.60