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	$170.95	5.152%	$179.7573	$179.76	$179.75	$179.80
Purchase #2	$97.63	5.615%	$103.1119	$103.11	$103.10	$103.10
Purchase #3	$27.31	3.531%	$28.2743	$28.27	$28.25	$28.30
Purchase #4	$230.80	8.474%	$250.358	$250.36	$250.35	$250.40
Purchase #5	$116.39	6.135%	$123.5305	$123.53	$123.55	$123.50
Purchase #6	$195.99	5.193%	$206.1678	$206.17	$206.15	$206.20
Purchase #7	$161.26	6.869%	$172.3369	$172.34	$172.35	$172.30
7 purchase totals =	$1,000.33		$1,063.5367	$1,063.54	$1,063.50	$1,063.60