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	$235.25	7.581%	$253.0843	$253.08	$253.10	$253.10
Purchase #2	$91.26	8.829%	$99.3173	$99.32	$99.30	$99.30
Purchase #3	$27.73	13.510%	$31.4763	$31.48	$31.50	$31.50
Purchase #4	$33.93	10.239%	$37.4041	$37.40	$37.40	$37.40
Purchase #5	$104.92	5.777%	$110.9812	$110.98	$111.00	$111.00
Purchase #6	$113.59	12.129%	$127.3673	$127.37	$127.35	$127.40
Purchase #7	$130.76	8.168%	$141.4405	$141.44	$141.45	$141.40
7 purchase totals =	$737.44		$801.0710	$801.07	$801.10	$801.10