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	$154.65	11.232%	$172.0203	$172.02	$172.00	$172.00
Purchase #2	$25.86	11.469%	$28.8259	$28.83	$28.85	$28.80
Purchase #3	$165.46	13.785%	$188.2687	$188.27	$188.25	$188.30
Purchase #4	$123.25	11.860%	$137.8675	$137.87	$137.85	$137.90
Purchase #5	$25.84	12.868%	$29.1651	$29.17	$29.15	$29.20
Purchase #6	$32.72	9.729%	$35.9033	$35.90	$35.90	$35.90
Purchase #7	$134.36	4.421%	$140.3001	$140.30	$140.30	$140.30
7 purchase totals =	$662.14		$732.3509	$732.36	$732.30	$732.40