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	$62.52	5.175%	$65.7554	$65.76	$65.75	$65.80
Purchase #2	$56.31	5.297%	$59.2927	$59.29	$59.30	$59.30
Purchase #3	$186.45	12.492%	$209.7413	$209.74	$209.75	$209.70
Purchase #4	$83.40	4.789%	$87.394	$87.39	$87.40	$87.40
Purchase #5	$166.92	13.570%	$189.571	$189.57	$189.55	$189.60
Purchase #6	$244.77	12.482%	$275.3222	$275.32	$275.30	$275.30
Purchase #7	$103.27	11.808%	$115.4641	$115.46	$115.45	$115.50
7 purchase totals =	$903.64		$1,002.5407	$1,002.53	$1,002.50	$1,002.60