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	$164.53	10.487%	$181.7843	$181.78	$181.80	$181.80
Purchase #2	$53.30	8.519%	$57.8406	$57.84	$57.85	$57.80
Purchase #3	$45.25	10.341%	$49.9293	$49.93	$49.95	$49.90
Purchase #4	$189.58	8.854%	$206.3654	$206.37	$206.35	$206.40
Purchase #5	$214.33	4.205%	$223.3426	$223.34	$223.35	$223.30
Purchase #6	$89.38	12.543%	$100.5909	$100.59	$100.60	$100.60
Purchase #7	$224.96	10.650%	$248.9182	$248.92	$248.90	$248.90
7 purchase totals =	$981.33		$1,068.7713	$1,068.77	$1,068.80	$1,068.70