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	$69.38	4.662%	$72.6145	$72.61	$72.60	$72.60
Purchase #2	$104.67	10.360%	$115.5138	$115.51	$115.50	$115.50
Purchase #3	$112.58	4.843%	$118.0322	$118.03	$118.05	$118.00
Purchase #4	$18.47	13.729%	$21.0057	$21.01	$21.00	$21.00
Purchase #5	$204.31	9.370%	$223.4538	$223.45	$223.45	$223.50
Purchase #6	$20.96	7.162%	$22.4612	$22.46	$22.45	$22.50
Purchase #7	$166.27	11.302%	$185.0618	$185.06	$185.05	$185.10
7 purchase totals =	$696.64		$758.1430	$758.13	$758.10	$758.20