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	$153.49	13.833%	$174.7223	$174.72	$174.70	$174.70
Purchase #2	$147.38	11.344%	$164.0988	$164.10	$164.10	$164.10
Purchase #3	$124.38	12.363%	$139.7571	$139.76	$139.75	$139.80
Purchase #4	$70.98	10.784%	$78.6345	$78.63	$78.65	$78.60
Purchase #5	$77.62	5.309%	$81.7408	$81.74	$81.75	$81.70
Purchase #6	$106.40	12.270%	$119.4553	$119.46	$119.45	$119.50
Purchase #7	$156.26	10.571%	$172.7782	$172.78	$172.80	$172.80
7 purchase totals =	$836.51		$931.1870	$931.19	$931.20	$931.20