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	$197.38	3.496%	$204.2804	$204.28	$204.30	$204.30
Purchase #2	$222.90	8.249%	$241.287	$241.29	$241.30	$241.30
Purchase #3	$238.77	11.650%	$266.5867	$266.59	$266.60	$266.60
Purchase #4	$218.56	5.807%	$231.2518	$231.25	$231.25	$231.30
Purchase #5	$196.83	6.349%	$209.3267	$209.33	$209.35	$209.30
Purchase #6	$89.77	10.634%	$99.3161	$99.32	$99.30	$99.30
Purchase #7	$174.62	7.472%	$187.6676	$187.67	$187.65	$187.70
7 purchase totals =	$1,338.83		$1,439.7163	$1,439.73	$1,439.75	$1,439.80