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	$156.72	10.109%	$172.5628	$172.56	$172.55	$172.60
Purchase #2	$80.31	4.442%	$83.8774	$83.88	$83.90	$83.90
Purchase #3	$61.89	5.795%	$65.4765	$65.48	$65.50	$65.50
Purchase #4	$170.76	13.667%	$194.0978	$194.10	$194.10	$194.10
Purchase #5	$32.80	6.771%	$35.0209	$35.02	$35.00	$35.00
Purchase #6	$88.27	5.387%	$93.0251	$93.03	$93.05	$93.00
Purchase #7	$243.47	8.433%	$264.0018	$264.00	$264.00	$264.00
7 purchase totals =	$834.22		$908.0623	$908.07	$908.10	$908.10