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	$92.71	10.731%	$102.6587	$102.66	$102.65	$102.70
Purchase #2	$168.70	9.729%	$185.1128	$185.11	$185.10	$185.10
Purchase #3	$128.91	4.562%	$134.7909	$134.79	$134.80	$134.80
Purchase #4	$222.58	10.141%	$245.1518	$245.15	$245.15	$245.20
Purchase #5	$40.65	11.520%	$45.3329	$45.33	$45.35	$45.30
Purchase #6	$250.34	12.135%	$280.7188	$280.72	$280.70	$280.70
Purchase #7	$147.72	8.496%	$160.2703	$160.27	$160.25	$160.30
7 purchase totals =	$1,051.61		$1,154.0362	$1,154.03	$1,154.00	$1,154.10