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	$182.82	4.317%	$190.7123	$190.71	$190.70	$190.70
Purchase #2	$125.64	13.290%	$142.3376	$142.34	$142.35	$142.30
Purchase #3	$46.96	9.726%	$51.5273	$51.53	$51.55	$51.50
Purchase #4	$209.30	5.479%	$220.7675	$220.77	$220.75	$220.80
Purchase #5	$191.65	13.144%	$216.8405	$216.84	$216.85	$216.80
Purchase #6	$54.73	9.176%	$59.752	$59.75	$59.75	$59.80
Purchase #7	$73.45	10.734%	$81.3341	$81.33	$81.35	$81.30
7 purchase totals =	$884.55		$963.2713	$963.27	$963.30	$963.20