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	$235.48	7.713%	$253.6426	$253.64	$253.65	$253.60
Purchase #2	$131.25	9.834%	$144.1571	$144.16	$144.15	$144.20
Purchase #3	$207.34	7.680%	$223.2637	$223.26	$223.25	$223.30
Purchase #4	$81.55	9.312%	$89.1439	$89.14	$89.15	$89.10
Purchase #5	$77.30	13.499%	$87.7347	$87.73	$87.75	$87.70
Purchase #6	$89.74	9.128%	$97.9315	$97.93	$97.95	$97.90
Purchase #7	$220.83	4.795%	$231.4188	$231.42	$231.40	$231.40
7 purchase totals =	$1,043.49		$1,127.2923	$1,127.28	$1,127.30	$1,127.20