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	$33.28	11.575%	$37.1322	$37.13	$37.15	$37.10
Purchase #2	$97.74	11.555%	$109.0339	$109.03	$109.05	$109.00
Purchase #3	$85.49	4.689%	$89.4986	$89.50	$89.50	$89.50
Purchase #4	$97.94	7.326%	$105.1151	$105.12	$105.10	$105.10
Purchase #5	$91.75	11.842%	$102.615	$102.62	$102.60	$102.60
Purchase #6	$113.32	10.439%	$125.1495	$125.15	$125.15	$125.10
Purchase #7	$222.73	9.786%	$244.5264	$244.53	$244.55	$244.50
7 purchase totals =	$742.25		$813.0707	$813.08	$813.10	$812.90