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	$47.88	13.104%	$54.1542	$54.15	$54.15	$54.20
Purchase #2	$204.58	6.550%	$217.98	$217.98	$218.00	$218.00
Purchase #3	$204.92	13.278%	$232.1293	$232.13	$232.15	$232.10
Purchase #4	$114.73	10.836%	$127.1621	$127.16	$127.15	$127.20
Purchase #5	$152.84	8.804%	$166.296	$166.30	$166.30	$166.30
Purchase #6	$158.27	13.518%	$179.6649	$179.66	$179.65	$179.70
Purchase #7	$135.36	10.847%	$150.0425	$150.04	$150.05	$150.00
7 purchase totals =	$1,018.58		$1,127.4290	$1,127.42	$1,127.45	$1,127.50