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	$106.26	11.187%	$118.1473	$118.15	$118.15	$118.10
Purchase #2	$48.45	13.272%	$54.8803	$54.88	$54.90	$54.90
Purchase #3	$186.71	13.630%	$212.1586	$212.16	$212.15	$212.20
Purchase #4	$105.96	13.844%	$120.6291	$120.63	$120.65	$120.60
Purchase #5	$209.82	6.365%	$223.175	$223.18	$223.20	$223.20
Purchase #6	$144.67	8.454%	$156.9004	$156.90	$156.90	$156.90
Purchase #7	$124.46	10.796%	$137.8967	$137.90	$137.90	$137.90
7 purchase totals =	$926.33		$1,023.7874	$1,023.80	$1,023.85	$1,023.80