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	$212.71	4.466%	$222.2096	$222.21	$222.20	$222.20
Purchase #2	$72.86	6.845%	$77.8473	$77.85	$77.85	$77.80
Purchase #3	$78.82	5.104%	$82.843	$82.84	$82.85	$82.80
Purchase #4	$80.72	11.857%	$90.291	$90.29	$90.30	$90.30
Purchase #5	$184.71	4.152%	$192.3792	$192.38	$192.40	$192.40
Purchase #6	$16.34	12.254%	$18.3423	$18.34	$18.35	$18.30
Purchase #7	$94.66	4.664%	$99.0749	$99.07	$99.05	$99.10
7 purchase totals =	$740.82		$782.9873	$782.98	$783.00	$782.90