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	$152.40	12.313%	$171.165	$171.17	$171.15	$171.20
Purchase #2	$49.34	7.632%	$53.1056	$53.11	$53.10	$53.10
Purchase #3	$60.60	7.257%	$64.9977	$65.00	$65.00	$65.00
Purchase #4	$237.52	13.591%	$269.8013	$269.80	$269.80	$269.80
Purchase #5	$141.66	6.260%	$150.5279	$150.53	$150.55	$150.50
Purchase #6	$169.79	12.855%	$191.6165	$191.62	$191.60	$191.60
Purchase #7	$205.61	10.116%	$226.4095	$226.41	$226.40	$226.40
7 purchase totals =	$1,016.92		$1,127.6235	$1,127.64	$1,127.60	$1,127.60