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	$236.42	7.254%	$253.5699	$253.57	$253.55	$253.60
Purchase #2	$83.33	11.563%	$92.9654	$92.97	$92.95	$93.00
Purchase #3	$118.26	10.331%	$130.4774	$130.48	$130.50	$130.50
Purchase #4	$213.89	4.354%	$223.2028	$223.20	$223.20	$223.20
Purchase #5	$239.69	10.465%	$264.7736	$264.77	$264.75	$264.80
Purchase #6	$80.86	11.356%	$90.0425	$90.04	$90.05	$90.00
Purchase #7	$22.41	9.116%	$24.4529	$24.45	$24.45	$24.50
7 purchase totals =	$994.86		$1,079.4845	$1,079.48	$1,079.45	$1,079.60