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	$42.85	3.380%	$44.2983	$44.30	$44.30	$44.30
Purchase #2	$40.51	11.236%	$45.0617	$45.06	$45.05	$45.10
Purchase #3	$25.35	11.709%	$28.3182	$28.32	$28.30	$28.30
Purchase #4	$178.30	12.104%	$199.8814	$199.88	$199.90	$199.90
Purchase #5	$171.33	11.627%	$191.2505	$191.25	$191.25	$191.30
Purchase #6	$224.81	13.617%	$255.4224	$255.42	$255.40	$255.40
Purchase #7	$171.74	7.313%	$184.2993	$184.30	$184.30	$184.30
7 purchase totals =	$854.89		$948.5318	$948.53	$948.50	$948.60