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	$147.59	5.741%	$156.0631	$156.06	$156.05	$156.10
Purchase #2	$184.79	5.256%	$194.5026	$194.50	$194.50	$194.50
Purchase #3	$141.53	10.612%	$156.5492	$156.55	$156.55	$156.50
Purchase #4	$228.92	6.828%	$244.5507	$244.55	$244.55	$244.60
Purchase #5	$172.58	7.281%	$185.1455	$185.15	$185.15	$185.10
Purchase #6	$250.55	4.533%	$261.9074	$261.91	$261.90	$261.90
Purchase #7	$97.73	7.803%	$105.3559	$105.36	$105.35	$105.40
7 purchase totals =	$1,223.69		$1,304.0744	$1,304.08	$1,304.05	$1,304.10