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	$65.72	11.369%	$73.1917	$73.19	$73.20	$73.20
Purchase #2	$228.76	6.138%	$242.8013	$242.80	$242.80	$242.80
Purchase #3	$143.91	5.866%	$152.3518	$152.35	$152.35	$152.40
Purchase #4	$89.95	12.403%	$101.1065	$101.11	$101.10	$101.10
Purchase #5	$38.32	5.395%	$40.3874	$40.39	$40.40	$40.40
Purchase #6	$48.32	13.364%	$54.7775	$54.78	$54.80	$54.80
Purchase #7	$92.68	4.488%	$96.8395	$96.84	$96.85	$96.80
7 purchase totals =	$707.66		$761.4557	$761.46	$761.50	$761.50