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	$133.70	5.572%	$141.1498	$141.15	$141.15	$141.10
Purchase #2	$46.58	3.161%	$48.0524	$48.05	$48.05	$48.10
Purchase #3	$245.73	4.125%	$255.8664	$255.87	$255.85	$255.90
Purchase #4	$63.68	11.603%	$71.0688	$71.07	$71.05	$71.10
Purchase #5	$134.45	8.399%	$145.7425	$145.74	$145.75	$145.70
Purchase #6	$196.96	6.489%	$209.7407	$209.74	$209.75	$209.70
Purchase #7	$134.27	10.627%	$148.5389	$148.54	$148.55	$148.50
7 purchase totals =	$955.37		$1,020.1595	$1,020.16	$1,020.15	$1,020.10