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	$167.85	3.282%	$173.3588	$173.36	$173.35	$173.40
Purchase #2	$195.54	11.212%	$217.4639	$217.46	$217.45	$217.50
Purchase #3	$179.79	11.260%	$200.0344	$200.03	$200.05	$200.00
Purchase #4	$181.40	3.697%	$188.1064	$188.11	$188.10	$188.10
Purchase #5	$133.38	13.435%	$151.2996	$151.30	$151.30	$151.30
Purchase #6	$91.99	8.816%	$100.0998	$100.10	$100.10	$100.10
Purchase #7	$19.61	6.855%	$20.9543	$20.95	$20.95	$21.00
7 purchase totals =	$969.56		$1,051.3172	$1,051.31	$1,051.30	$1,051.40