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	$152.33	5.580%	$160.83	$160.83	$160.85	$160.80
Purchase #2	$247.85	7.377%	$266.1339	$266.13	$266.15	$266.10
Purchase #3	$41.99	10.781%	$46.5169	$46.52	$46.50	$46.50
Purchase #4	$247.42	3.566%	$256.243	$256.24	$256.25	$256.20
Purchase #5	$250.51	7.498%	$269.2932	$269.29	$269.30	$269.30
Purchase #6	$181.41	5.788%	$191.91	$191.91	$191.90	$191.90
Purchase #7	$192.53	10.871%	$213.4599	$213.46	$213.45	$213.50
7 purchase totals =	$1,314.04		$1,404.3869	$1,404.38	$1,404.40	$1,404.30