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	$21.70	3.168%	$22.3875	$22.39	$22.40	$22.40
Purchase #2	$205.56	5.798%	$217.4784	$217.48	$217.50	$217.50
Purchase #3	$248.40	6.527%	$264.6131	$264.61	$264.60	$264.60
Purchase #4	$45.69	11.397%	$50.8973	$50.90	$50.90	$50.90
Purchase #5	$190.85	4.589%	$199.6081	$199.61	$199.60	$199.60
Purchase #6	$109.32	5.314%	$115.1293	$115.13	$115.15	$115.10
Purchase #7	$199.68	10.860%	$221.3652	$221.37	$221.35	$221.40
7 purchase totals =	$1,021.20		$1,091.4789	$1,091.49	$1,091.50	$1,091.50