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	$165.29	4.124%	$172.1066	$172.11	$172.10	$172.10
Purchase #2	$34.47	9.174%	$37.6323	$37.63	$37.65	$37.60
Purchase #3	$51.59	3.146%	$53.213	$53.21	$53.20	$53.20
Purchase #4	$114.76	11.117%	$127.5179	$127.52	$127.50	$127.50
Purchase #5	$105.73	13.831%	$120.3535	$120.35	$120.35	$120.40
Purchase #6	$240.31	3.605%	$248.9732	$248.97	$248.95	$249.00
Purchase #7	$168.51	11.783%	$188.3655	$188.37	$188.35	$188.40
7 purchase totals =	$880.66		$948.1620	$948.16	$948.10	$948.20