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	$112.51	10.677%	$124.5227	$124.52	$124.50	$124.50
Purchase #2	$121.38	8.151%	$131.2737	$131.27	$131.25	$131.30
Purchase #3	$36.74	10.625%	$40.6436	$40.64	$40.65	$40.60
Purchase #4	$235.69	8.755%	$256.3247	$256.32	$256.30	$256.30
Purchase #5	$120.91	8.697%	$131.4255	$131.43	$131.45	$131.40
Purchase #6	$235.61	4.139%	$245.3619	$245.36	$245.35	$245.40
Purchase #7	$223.46	7.373%	$239.9357	$239.94	$239.95	$239.90
7 purchase totals =	$1,086.30		$1,169.4878	$1,169.48	$1,169.45	$1,169.40