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	$172.50	7.759%	$185.8843	$185.88	$185.90	$185.90
Purchase #2	$87.51	13.499%	$99.323	$99.32	$99.30	$99.30
Purchase #3	$91.46	11.451%	$101.9331	$101.93	$101.95	$101.90
Purchase #4	$87.71	11.618%	$97.9001	$97.90	$97.90	$97.90
Purchase #5	$119.33	13.212%	$135.0959	$135.10	$135.10	$135.10
Purchase #6	$93.71	12.864%	$105.7649	$105.76	$105.75	$105.80
Purchase #7	$26.95	5.288%	$28.3751	$28.38	$28.40	$28.40
7 purchase totals =	$679.17		$754.2764	$754.27	$754.30	$754.30