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	$223.64	4.592%	$233.9095	$233.91	$233.90	$233.90
Purchase #2	$155.88	4.453%	$162.8213	$162.82	$162.80	$162.80
Purchase #3	$93.36	11.308%	$103.9171	$103.92	$103.90	$103.90
Purchase #4	$79.51	13.724%	$90.422	$90.42	$90.40	$90.40
Purchase #5	$179.43	4.325%	$187.1903	$187.19	$187.20	$187.20
Purchase #6	$141.80	6.247%	$150.6582	$150.66	$150.65	$150.70
Purchase #7	$183.57	9.841%	$201.6351	$201.64	$201.65	$201.60
7 purchase totals =	$1,057.19		$1,130.5535	$1,130.56	$1,130.50	$1,130.50