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	$62.35	11.547%	$69.5496	$69.55	$69.55	$69.50
Purchase #2	$94.27	4.610%	$98.6158	$98.62	$98.60	$98.60
Purchase #3	$175.28	9.288%	$191.56	$191.56	$191.55	$191.60
Purchase #4	$250.64	3.738%	$260.0089	$260.01	$260.00	$260.00
Purchase #5	$119.47	7.542%	$128.4804	$128.48	$128.50	$128.50
Purchase #6	$101.73	3.332%	$105.1196	$105.12	$105.10	$105.10
Purchase #7	$237.65	11.419%	$264.7873	$264.79	$264.80	$264.80
7 purchase totals =	$1,041.39		$1,118.1216	$1,118.13	$1,118.10	$1,118.10