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	$83.53	3.315%	$86.299	$86.30	$86.30	$86.30
Purchase #2	$130.38	3.183%	$134.53	$134.53	$134.55	$134.50
Purchase #3	$157.77	8.373%	$170.9801	$170.98	$171.00	$171.00
Purchase #4	$248.72	10.173%	$274.0223	$274.02	$274.00	$274.00
Purchase #5	$189.39	10.201%	$208.7097	$208.71	$208.70	$208.70
Purchase #6	$34.75	7.345%	$37.3024	$37.30	$37.30	$37.30
Purchase #7	$174.71	7.771%	$188.2867	$188.29	$188.30	$188.30
7 purchase totals =	$1,019.25		$1,100.1302	$1,100.13	$1,100.15	$1,100.10