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	$104.91	6.382%	$111.6054	$111.61	$111.60	$111.60
Purchase #2	$175.45	6.210%	$186.3454	$186.35	$186.35	$186.30
Purchase #3	$179.40	3.464%	$185.6144	$185.61	$185.60	$185.60
Purchase #4	$85.46	4.519%	$89.3219	$89.32	$89.30	$89.30
Purchase #5	$195.34	8.393%	$211.7349	$211.73	$211.75	$211.70
Purchase #6	$152.95	12.526%	$172.1085	$172.11	$172.10	$172.10
Purchase #7	$170.68	8.282%	$184.8157	$184.82	$184.80	$184.80
7 purchase totals =	$1,064.19		$1,141.5462	$1,141.55	$1,141.50	$1,141.40