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	$158.77	6.758%	$169.4997	$169.50	$169.50	$169.50
Purchase #2	$123.52	3.348%	$127.6554	$127.66	$127.65	$127.70
Purchase #3	$150.55	7.618%	$162.0189	$162.02	$162.00	$162.00
Purchase #4	$193.91	13.310%	$219.7194	$219.72	$219.70	$219.70
Purchase #5	$151.51	10.372%	$167.2246	$167.22	$167.20	$167.20
Purchase #6	$112.39	11.317%	$125.1092	$125.11	$125.10	$125.10
Purchase #7	$102.43	10.798%	$113.4904	$113.49	$113.50	$113.50
7 purchase totals =	$993.08		$1,084.7176	$1,084.72	$1,084.65	$1,084.70