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	$145.45	3.547%	$150.6091	$150.61	$150.60	$150.60
Purchase #2	$62.40	8.601%	$67.767	$67.77	$67.75	$67.80
Purchase #3	$35.62	5.113%	$37.4413	$37.44	$37.45	$37.40
Purchase #4	$44.33	11.220%	$49.3038	$49.30	$49.30	$49.30
Purchase #5	$71.92	4.709%	$75.3067	$75.31	$75.30	$75.30
Purchase #6	$156.49	6.807%	$167.1423	$167.14	$167.15	$167.10
Purchase #7	$170.84	10.567%	$188.8927	$188.89	$188.90	$188.90
7 purchase totals =	$687.05		$736.4629	$736.46	$736.45	$736.40