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	$183.34	3.705%	$190.1327	$190.13	$190.15	$190.10
Purchase #2	$209.41	11.471%	$233.4314	$233.43	$233.45	$233.40
Purchase #3	$123.65	9.593%	$135.5117	$135.51	$135.50	$135.50
Purchase #4	$96.34	5.172%	$101.3227	$101.32	$101.30	$101.30
Purchase #5	$188.44	6.201%	$200.1252	$200.13	$200.15	$200.10
Purchase #6	$103.67	8.819%	$112.8127	$112.81	$112.80	$112.80
Purchase #7	$46.82	11.695%	$52.2956	$52.30	$52.30	$52.30
7 purchase totals =	$951.67		$1,025.6320	$1,025.63	$1,025.65	$1,025.50