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	$189.26	11.456%	$210.9416	$210.94	$210.95	$210.90
Purchase #2	$140.61	10.355%	$155.1702	$155.17	$155.15	$155.20
Purchase #3	$233.40	9.393%	$255.3233	$255.32	$255.30	$255.30
Purchase #4	$223.28	12.481%	$251.1476	$251.15	$251.15	$251.10
Purchase #5	$63.39	7.532%	$68.1645	$68.16	$68.15	$68.20
Purchase #6	$89.59	12.311%	$100.6194	$100.62	$100.60	$100.60
Purchase #7	$6.38	11.550%	$7.1169	$7.12	$7.10	$7.10
7 purchase totals =	$945.91		$1,048.4835	$1,048.48	$1,048.40	$1,048.40