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	$97.32	8.828%	$105.9114	$105.91	$105.90	$105.90
Purchase #2	$111.95	8.816%	$121.8195	$121.82	$121.80	$121.80
Purchase #3	$83.91	8.329%	$90.8989	$90.90	$90.90	$90.90
Purchase #4	$86.48	6.449%	$92.0571	$92.06	$92.05	$92.10
Purchase #5	$222.26	12.704%	$250.4959	$250.50	$250.50	$250.50
Purchase #6	$227.56	11.332%	$253.3471	$253.35	$253.35	$253.30
Purchase #7	$106.74	4.701%	$111.7578	$111.76	$111.75	$111.80
7 purchase totals =	$936.22		$1,026.2877	$1,026.30	$1,026.25	$1,026.30