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	$134.76	5.337%	$141.9521	$141.95	$141.95	$142.00
Purchase #2	$33.64	10.395%	$37.1369	$37.14	$37.15	$37.10
Purchase #3	$152.80	7.487%	$164.2401	$164.24	$164.25	$164.20
Purchase #4	$150.55	9.244%	$164.4668	$164.47	$164.45	$164.50
Purchase #5	$92.33	10.729%	$102.2361	$102.24	$102.25	$102.20
Purchase #6	$244.71	12.742%	$275.8909	$275.89	$275.90	$275.90
Purchase #7	$209.50	4.115%	$218.1209	$218.12	$218.10	$218.10
7 purchase totals =	$1,018.29		$1,104.0438	$1,104.05	$1,104.05	$1,104.00