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	$98.60	7.284%	$105.782	$105.78	$105.80	$105.80
Purchase #2	$20.45	5.113%	$21.4956	$21.50	$21.50	$21.50
Purchase #3	$78.44	12.842%	$88.5133	$88.51	$88.50	$88.50
Purchase #4	$27.51	6.501%	$29.2984	$29.30	$29.30	$29.30
Purchase #5	$171.76	4.254%	$179.0667	$179.07	$179.05	$179.10
Purchase #6	$176.26	10.448%	$194.6756	$194.68	$194.70	$194.70
Purchase #7	$149.66	11.316%	$166.5955	$166.60	$166.60	$166.60
7 purchase totals =	$722.68		$785.4271	$785.44	$785.45	$785.50