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	$245.89	7.466%	$264.2481	$264.25	$264.25	$264.20
Purchase #2	$146.61	10.533%	$162.0524	$162.05	$162.05	$162.10
Purchase #3	$6.75	9.246%	$7.3741	$7.37	$7.35	$7.40
Purchase #4	$151.89	10.372%	$167.644	$167.64	$167.65	$167.60
Purchase #5	$200.68	4.418%	$209.546	$209.55	$209.55	$209.50
Purchase #6	$87.28	6.574%	$93.0178	$93.02	$93.00	$93.00
Purchase #7	$164.41	3.829%	$170.7053	$170.71	$170.70	$170.70
7 purchase totals =	$1,003.51		$1,074.5877	$1,074.59	$1,074.55	$1,074.50