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	$152.59	9.613%	$167.2585	$167.26	$167.25	$167.30
Purchase #2	$92.52	7.272%	$99.2481	$99.25	$99.25	$99.20
Purchase #3	$65.57	12.584%	$73.8213	$73.82	$73.80	$73.80
Purchase #4	$87.67	13.761%	$99.7343	$99.73	$99.75	$99.70
Purchase #5	$145.32	11.776%	$162.4329	$162.43	$162.45	$162.40
Purchase #6	$60.40	8.323%	$65.4271	$65.43	$65.45	$65.40
Purchase #7	$211.35	8.636%	$229.6022	$229.60	$229.60	$229.60
7 purchase totals =	$815.42		$897.5244	$897.52	$897.55	$897.40