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	$168.92	11.607%	$188.5265	$188.53	$188.55	$188.50
Purchase #2	$7.37	4.642%	$7.7121	$7.71	$7.70	$7.70
Purchase #3	$237.96	5.196%	$250.3244	$250.32	$250.30	$250.30
Purchase #4	$84.76	8.152%	$91.6696	$91.67	$91.65	$91.70
Purchase #5	$162.48	9.728%	$178.2861	$178.29	$178.30	$178.30
Purchase #6	$103.56	12.799%	$116.8146	$116.81	$116.80	$116.80
Purchase #7	$224.72	13.344%	$254.7066	$254.71	$254.70	$254.70
7 purchase totals =	$989.77		$1,088.0399	$1,088.04	$1,088.00	$1,088.00