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	$62.52	3.843%	$64.9226	$64.92	$64.90	$64.90
Purchase #2	$186.89	5.250%	$196.7017	$196.70	$196.70	$196.70
Purchase #3	$69.52	4.843%	$72.8869	$72.89	$72.90	$72.90
Purchase #4	$181.41	5.339%	$191.0955	$191.10	$191.10	$191.10
Purchase #5	$57.30	6.274%	$60.895	$60.90	$60.90	$60.90
Purchase #6	$121.60	10.611%	$134.503	$134.50	$134.50	$134.50
Purchase #7	$215.55	10.289%	$237.7279	$237.73	$237.75	$237.70
7 purchase totals =	$894.79		$958.7326	$958.74	$958.75	$958.70