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	$125.57	11.757%	$140.3333	$140.33	$140.35	$140.30
Purchase #2	$37.83	11.435%	$42.1559	$42.16	$42.15	$42.20
Purchase #3	$103.41	4.632%	$108.2	$108.20	$108.20	$108.20
Purchase #4	$48.84	4.234%	$50.9079	$50.91	$50.90	$50.90
Purchase #5	$20.56	13.693%	$23.3753	$23.38	$23.40	$23.40
Purchase #6	$42.35	4.764%	$44.3676	$44.37	$44.35	$44.40
Purchase #7	$26.47	3.372%	$27.3626	$27.36	$27.35	$27.40
7 purchase totals =	$405.03		$436.7026	$436.71	$436.70	$436.80