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	$181.50	9.278%	$198.3396	$198.34	$198.35	$198.30
Purchase #2	$112.68	12.729%	$127.023	$127.02	$127.00	$127.00
Purchase #3	$37.79	9.115%	$41.2346	$41.23	$41.25	$41.20
Purchase #4	$173.83	4.294%	$181.2943	$181.29	$181.30	$181.30
Purchase #5	$92.39	7.723%	$99.5253	$99.53	$99.55	$99.50
Purchase #6	$114.88	10.710%	$127.1836	$127.18	$127.20	$127.20
Purchase #7	$147.44	10.243%	$162.5423	$162.54	$162.55	$162.50
7 purchase totals =	$860.51		$937.1427	$937.13	$937.20	$937.00