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	$241.56	4.290%	$251.9229	$251.92	$251.90	$251.90
Purchase #2	$79.26	3.669%	$82.168	$82.17	$82.15	$82.20
Purchase #3	$159.28	12.671%	$179.4624	$179.46	$179.45	$179.50
Purchase #4	$83.49	11.787%	$93.331	$93.33	$93.35	$93.30
Purchase #5	$148.62	10.702%	$164.5253	$164.53	$164.55	$164.50
Purchase #6	$10.99	11.850%	$12.2923	$12.29	$12.30	$12.30
Purchase #7	$86.83	6.656%	$92.6094	$92.61	$92.60	$92.60
7 purchase totals =	$810.03		$876.3113	$876.31	$876.30	$876.30