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	$171.33	13.554%	$194.5521	$194.55	$194.55	$194.60
Purchase #2	$120.75	11.109%	$134.1641	$134.16	$134.15	$134.20
Purchase #3	$191.67	11.548%	$213.8041	$213.80	$213.80	$213.80
Purchase #4	$80.86	8.842%	$88.0096	$88.01	$88.00	$88.00
Purchase #5	$89.61	12.637%	$100.934	$100.93	$100.95	$100.90
Purchase #6	$74.74	9.623%	$81.9322	$81.93	$81.95	$81.90
Purchase #7	$153.61	7.392%	$164.9649	$164.96	$164.95	$165.00
7 purchase totals =	$882.57		$978.3610	$978.34	$978.35	$978.40