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	$177.55	10.474%	$196.1466	$196.15	$196.15	$196.10
Purchase #2	$88.86	12.349%	$99.8333	$99.83	$99.85	$99.80
Purchase #3	$64.40	10.306%	$71.0371	$71.04	$71.05	$71.00
Purchase #4	$155.87	5.413%	$164.3072	$164.31	$164.30	$164.30
Purchase #5	$145.94	8.770%	$158.7389	$158.74	$158.75	$158.70
Purchase #6	$149.85	4.717%	$156.9184	$156.92	$156.90	$156.90
Purchase #7	$143.92	6.545%	$153.3396	$153.34	$153.35	$153.30
7 purchase totals =	$926.39		$1,000.3211	$1,000.33	$1,000.35	$1,000.10