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	$229.54	8.335%	$248.6722	$248.67	$248.65	$248.70
Purchase #2	$81.53	4.790%	$85.4353	$85.44	$85.45	$85.40
Purchase #3	$115.40	11.343%	$128.4898	$128.49	$128.50	$128.50
Purchase #4	$92.50	8.462%	$100.3274	$100.33	$100.35	$100.30
Purchase #5	$141.82	13.274%	$160.6452	$160.65	$160.65	$160.60
Purchase #6	$114.87	9.219%	$125.4599	$125.46	$125.45	$125.50
Purchase #7	$250.40	11.156%	$278.3346	$278.33	$278.35	$278.30
7 purchase totals =	$1,026.06		$1,127.3644	$1,127.37	$1,127.40	$1,127.30