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	$28.92	9.774%	$31.7466	$31.75	$31.75	$31.70
Purchase #2	$95.51	4.234%	$99.5539	$99.55	$99.55	$99.60
Purchase #3	$93.80	3.572%	$97.1505	$97.15	$97.15	$97.20
Purchase #4	$134.50	9.214%	$146.8928	$146.89	$146.90	$146.90
Purchase #5	$158.32	5.824%	$167.5406	$167.54	$167.55	$167.50
Purchase #6	$180.85	8.395%	$196.0324	$196.03	$196.05	$196.00
Purchase #7	$21.27	3.205%	$21.9517	$21.95	$21.95	$22.00
7 purchase totals =	$713.17		$760.8685	$760.86	$760.90	$760.90