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	$113.46	12.420%	$127.5517	$127.55	$127.55	$127.60
Purchase #2	$240.53	9.855%	$264.2342	$264.23	$264.25	$264.20
Purchase #3	$93.94	7.816%	$101.2824	$101.28	$101.30	$101.30
Purchase #4	$35.59	5.637%	$37.5962	$37.60	$37.60	$37.60
Purchase #5	$85.48	11.864%	$95.6213	$95.62	$95.60	$95.60
Purchase #6	$208.72	12.141%	$234.0607	$234.06	$234.05	$234.10
Purchase #7	$218.80	6.482%	$232.9826	$232.98	$233.00	$233.00
7 purchase totals =	$996.52		$1,093.3291	$1,093.32	$1,093.35	$1,093.40