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	$151.54	5.835%	$160.3824	$160.38	$160.40	$160.40
Purchase #2	$56.30	4.566%	$58.8707	$58.87	$58.85	$58.90
Purchase #3	$147.64	4.657%	$154.5156	$154.52	$154.50	$154.50
Purchase #4	$71.67	9.791%	$78.6872	$78.69	$78.70	$78.70
Purchase #5	$200.75	12.648%	$226.1409	$226.14	$226.15	$226.10
Purchase #6	$118.89	7.168%	$127.412	$127.41	$127.40	$127.40
Purchase #7	$170.72	13.662%	$194.0438	$194.04	$194.05	$194.00
7 purchase totals =	$917.51		$1,000.0526	$1,000.05	$1,000.05	$1,000.00