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	$139.92	7.444%	$150.3356	$150.34	$150.35	$150.30
Purchase #2	$205.30	11.247%	$228.3901	$228.39	$228.40	$228.40
Purchase #3	$147.78	6.624%	$157.5689	$157.57	$157.55	$157.60
Purchase #4	$212.88	7.867%	$229.6273	$229.63	$229.65	$229.60
Purchase #5	$123.33	6.586%	$131.4525	$131.45	$131.45	$131.50
Purchase #6	$41.77	8.777%	$45.4362	$45.44	$45.45	$45.40
Purchase #7	$98.88	4.488%	$103.3177	$103.32	$103.30	$103.30
7 purchase totals =	$969.86		$1,046.1283	$1,046.14	$1,046.15	$1,046.10