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	$147.80	11.754%	$165.1724	$165.17	$165.15	$165.20
Purchase #2	$44.74	4.673%	$46.8307	$46.83	$46.85	$46.80
Purchase #3	$67.34	6.686%	$71.8424	$71.84	$71.85	$71.80
Purchase #4	$103.71	4.165%	$108.0295	$108.03	$108.05	$108.00
Purchase #5	$51.65	4.321%	$53.8818	$53.88	$53.90	$53.90
Purchase #6	$187.31	11.820%	$209.45	$209.45	$209.45	$209.50
Purchase #7	$161.67	7.584%	$173.9311	$173.93	$173.95	$173.90
7 purchase totals =	$764.22		$829.1379	$829.13	$829.20	$829.10