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	$185.43	4.835%	$194.3955	$194.40	$194.40	$194.40
Purchase #2	$170.77	11.805%	$190.9294	$190.93	$190.95	$190.90
Purchase #3	$209.69	6.295%	$222.89	$222.89	$222.90	$222.90
Purchase #4	$6.68	10.610%	$7.3887	$7.39	$7.40	$7.40
Purchase #5	$44.62	12.630%	$50.2555	$50.26	$50.25	$50.30
Purchase #6	$223.67	8.663%	$243.0465	$243.05	$243.05	$243.00
Purchase #7	$210.48	11.551%	$234.7925	$234.79	$234.80	$234.80
7 purchase totals =	$1,051.34		$1,143.6981	$1,143.71	$1,143.75	$1,143.70