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	$49.31	12.353%	$55.4013	$55.40	$55.40	$55.40
Purchase #2	$94.84	11.321%	$105.5768	$105.58	$105.60	$105.60
Purchase #3	$86.77	3.564%	$89.8625	$89.86	$89.85	$89.90
Purchase #4	$229.55	6.412%	$244.2687	$244.27	$244.25	$244.30
Purchase #5	$141.28	7.136%	$151.3617	$151.36	$151.35	$151.40
Purchase #6	$212.53	5.302%	$223.7983	$223.80	$223.80	$223.80
Purchase #7	$95.43	6.855%	$101.9717	$101.97	$101.95	$102.00
7 purchase totals =	$909.71		$972.2410	$972.24	$972.20	$972.40