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	$134.31	6.752%	$143.3786	$143.38	$143.40	$143.40
Purchase #2	$152.64	4.820%	$159.9972	$160.00	$160.00	$160.00
Purchase #3	$135.70	11.806%	$151.7207	$151.72	$151.70	$151.70
Purchase #4	$169.33	13.760%	$192.6298	$192.63	$192.65	$192.60
Purchase #5	$76.31	5.491%	$80.5002	$80.50	$80.50	$80.50
Purchase #6	$196.51	7.139%	$210.5388	$210.54	$210.55	$210.50
Purchase #7	$62.74	13.698%	$71.3341	$71.33	$71.35	$71.30
7 purchase totals =	$927.54		$1,010.0994	$1,010.10	$1,010.15	$1,010.00