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	$79.42	5.199%	$83.549	$83.55	$83.55	$83.50
Purchase #2	$120.65	4.302%	$125.8404	$125.84	$125.85	$125.80
Purchase #3	$156.41	13.854%	$178.079	$178.08	$178.10	$178.10
Purchase #4	$42.78	10.230%	$47.1564	$47.16	$47.15	$47.20
Purchase #5	$89.27	11.560%	$99.5896	$99.59	$99.60	$99.60
Purchase #6	$35.47	5.299%	$37.3496	$37.35	$37.35	$37.30
Purchase #7	$148.69	3.356%	$153.68	$153.68	$153.70	$153.70
7 purchase totals =	$672.69		$725.2440	$725.25	$725.30	$725.20