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	$192.61	7.823%	$207.6779	$207.68	$207.70	$207.70
Purchase #2	$60.76	5.744%	$64.2501	$64.25	$64.25	$64.30
Purchase #3	$90.33	10.192%	$99.5364	$99.54	$99.55	$99.50
Purchase #4	$36.59	11.333%	$40.7367	$40.74	$40.75	$40.70
Purchase #5	$223.51	12.177%	$250.7268	$250.73	$250.75	$250.70
Purchase #6	$196.50	7.173%	$210.5949	$210.59	$210.60	$210.60
Purchase #7	$135.25	7.300%	$145.1233	$145.12	$145.10	$145.10
7 purchase totals =	$935.55		$1,018.6461	$1,018.65	$1,018.70	$1,018.60