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	$72.97	12.753%	$82.2759	$82.28	$82.30	$82.30
Purchase #2	$106.71	3.250%	$110.1781	$110.18	$110.20	$110.20
Purchase #3	$189.88	8.702%	$206.4034	$206.40	$206.40	$206.40
Purchase #4	$175.66	11.868%	$196.5073	$196.51	$196.50	$196.50
Purchase #5	$149.87	5.740%	$158.4725	$158.47	$158.45	$158.50
Purchase #6	$143.67	13.407%	$162.9318	$162.93	$162.95	$162.90
Purchase #7	$27.37	5.174%	$28.7861	$28.79	$28.80	$28.80
7 purchase totals =	$866.13		$945.5551	$945.56	$945.60	$945.60