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	$183.61	3.541%	$190.1116	$190.11	$190.10	$190.10
Purchase #2	$40.66	13.452%	$46.1296	$46.13	$46.15	$46.10
Purchase #3	$135.60	11.127%	$150.6882	$150.69	$150.70	$150.70
Purchase #4	$173.40	6.839%	$185.2588	$185.26	$185.25	$185.30
Purchase #5	$99.63	5.122%	$104.733	$104.73	$104.75	$104.70
Purchase #6	$92.95	5.449%	$98.0148	$98.01	$98.00	$98.00
Purchase #7	$219.69	13.865%	$250.15	$250.15	$250.15	$250.20
7 purchase totals =	$945.54		$1,025.0860	$1,025.08	$1,025.10	$1,025.10