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	$236.48	4.337%	$246.7361	$246.74	$246.75	$246.70
Purchase #2	$56.39	10.677%	$62.4108	$62.41	$62.40	$62.40
Purchase #3	$206.34	8.135%	$223.1258	$223.13	$223.15	$223.10
Purchase #4	$103.49	3.118%	$106.7168	$106.72	$106.70	$106.70
Purchase #5	$147.70	5.469%	$155.7777	$155.78	$155.80	$155.80
Purchase #6	$101.98	9.715%	$111.8874	$111.89	$111.90	$111.90
Purchase #7	$160.48	4.839%	$168.2456	$168.25	$168.25	$168.20
7 purchase totals =	$1,012.86		$1,074.9002	$1,074.92	$1,074.95	$1,074.80