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	$77.77	11.530%	$86.7369	$86.74	$86.75	$86.70
Purchase #2	$190.69	4.127%	$198.5598	$198.56	$198.55	$198.60
Purchase #3	$155.94	7.700%	$167.9474	$167.95	$167.95	$167.90
Purchase #4	$74.77	4.657%	$78.252	$78.25	$78.25	$78.30
Purchase #5	$75.91	13.557%	$86.2011	$86.20	$86.20	$86.20
Purchase #6	$83.59	6.815%	$89.2867	$89.29	$89.30	$89.30
Purchase #7	$191.63	6.761%	$204.5861	$204.59	$204.60	$204.60
7 purchase totals =	$850.30		$911.5700	$911.58	$911.60	$911.60