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	$230.97	6.140%	$245.1516	$245.15	$245.15	$245.20
Purchase #2	$84.73	8.629%	$92.0414	$92.04	$92.05	$92.00
Purchase #3	$218.55	12.147%	$245.0973	$245.10	$245.10	$245.10
Purchase #4	$149.46	12.592%	$168.28	$168.28	$168.30	$168.30
Purchase #5	$79.46	13.650%	$90.3063	$90.31	$90.30	$90.30
Purchase #6	$163.97	10.695%	$181.5066	$181.51	$181.50	$181.50
Purchase #7	$167.82	9.335%	$183.486	$183.49	$183.50	$183.50
7 purchase totals =	$1,094.96		$1,205.8692	$1,205.88	$1,205.90	$1,205.90