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	$43.42	7.686%	$46.7573	$46.76	$46.75	$46.80
Purchase #2	$90.77	9.338%	$99.2461	$99.25	$99.25	$99.20
Purchase #3	$201.94	7.769%	$217.6287	$217.63	$217.65	$217.60
Purchase #4	$160.48	5.453%	$169.231	$169.23	$169.25	$169.20
Purchase #5	$147.88	11.614%	$165.0548	$165.05	$165.05	$165.10
Purchase #6	$182.28	7.597%	$196.1278	$196.13	$196.15	$196.10
Purchase #7	$231.98	10.248%	$255.7533	$255.75	$255.75	$255.80
7 purchase totals =	$1,058.75		$1,149.7990	$1,149.80	$1,149.85	$1,149.80