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	$130.98	12.729%	$147.6524	$147.65	$147.65	$147.70
Purchase #2	$58.43	11.389%	$65.0846	$65.08	$65.10	$65.10
Purchase #3	$44.77	12.399%	$50.321	$50.32	$50.30	$50.30
Purchase #4	$151.63	10.499%	$167.5496	$167.55	$167.55	$167.50
Purchase #5	$6.71	12.112%	$7.5227	$7.52	$7.50	$7.50
Purchase #6	$213.55	11.486%	$238.0784	$238.08	$238.10	$238.10
Purchase #7	$118.98	3.680%	$123.3585	$123.36	$123.35	$123.40
7 purchase totals =	$725.05		$799.5672	$799.56	$799.55	$799.60