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	$87.52	12.304%	$98.2885	$98.29	$98.30	$98.30
Purchase #2	$171.32	7.837%	$184.7463	$184.75	$184.75	$184.70
Purchase #3	$190.67	11.749%	$213.0718	$213.07	$213.05	$213.10
Purchase #4	$123.49	3.869%	$128.2678	$128.27	$128.25	$128.30
Purchase #5	$104.64	11.318%	$116.4832	$116.48	$116.50	$116.50
Purchase #6	$213.75	4.418%	$223.1935	$223.19	$223.20	$223.20
Purchase #7	$53.62	3.859%	$55.6892	$55.69	$55.70	$55.70
7 purchase totals =	$945.01		$1,019.7403	$1,019.74	$1,019.75	$1,019.80