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	$164.74	12.381%	$185.1365	$185.14	$185.15	$185.10
Purchase #2	$249.69	6.507%	$265.9373	$265.94	$265.95	$265.90
Purchase #3	$196.78	13.793%	$223.9219	$223.92	$223.90	$223.90
Purchase #4	$102.77	11.778%	$114.8743	$114.87	$114.85	$114.90
Purchase #5	$113.28	5.833%	$119.8876	$119.89	$119.90	$119.90
Purchase #6	$188.98	4.476%	$197.4387	$197.44	$197.45	$197.40
Purchase #7	$250.59	5.660%	$264.7734	$264.77	$264.75	$264.80
7 purchase totals =	$1,266.83		$1,371.9697	$1,371.97	$1,371.95	$1,371.90