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	$91.38	12.778%	$103.0565	$103.06	$103.05	$103.10
Purchase #2	$93.76	5.777%	$99.1765	$99.18	$99.20	$99.20
Purchase #3	$6.31	4.825%	$6.6145	$6.61	$6.60	$6.60
Purchase #4	$97.75	4.250%	$101.9044	$101.90	$101.90	$101.90
Purchase #5	$175.49	7.731%	$189.0571	$189.06	$189.05	$189.10
Purchase #6	$228.89	10.550%	$253.0379	$253.04	$253.05	$253.00
Purchase #7	$93.28	7.370%	$100.1547	$100.15	$100.15	$100.20
7 purchase totals =	$786.86		$853.0016	$853.00	$853.00	$853.10