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	$220.98	5.537%	$233.2157	$233.22	$233.20	$233.20
Purchase #2	$208.40	11.236%	$231.8158	$231.82	$231.80	$231.80
Purchase #3	$230.25	5.740%	$243.4664	$243.47	$243.45	$243.50
Purchase #4	$232.32	13.779%	$264.3314	$264.33	$264.35	$264.30
Purchase #5	$27.92	11.216%	$31.0515	$31.05	$31.05	$31.10
Purchase #6	$51.36	5.213%	$54.0374	$54.04	$54.05	$54.00
Purchase #7	$146.58	13.700%	$166.6615	$166.66	$166.65	$166.70
7 purchase totals =	$1,117.81		$1,224.5797	$1,224.59	$1,224.55	$1,224.60