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	$170.62	8.451%	$185.0391	$185.04	$185.05	$185.00
Purchase #2	$90.72	9.438%	$99.2822	$99.28	$99.30	$99.30
Purchase #3	$223.40	13.380%	$253.2909	$253.29	$253.30	$253.30
Purchase #4	$240.45	12.425%	$270.3259	$270.33	$270.35	$270.30
Purchase #5	$73.56	11.413%	$81.9554	$81.96	$81.95	$82.00
Purchase #6	$121.40	5.521%	$128.1025	$128.10	$128.10	$128.10
Purchase #7	$65.33	6.392%	$69.5059	$69.51	$69.50	$69.50
7 purchase totals =	$985.48		$1,087.5019	$1,087.51	$1,087.55	$1,087.50