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	$173.33	10.327%	$191.2298	$191.23	$191.25	$191.20
Purchase #2	$129.37	10.426%	$142.8581	$142.86	$142.85	$142.90
Purchase #3	$163.96	5.288%	$172.6302	$172.63	$172.65	$172.60
Purchase #4	$32.59	8.179%	$35.2555	$35.26	$35.25	$35.30
Purchase #5	$166.53	10.160%	$183.4494	$183.45	$183.45	$183.40
Purchase #6	$230.75	8.372%	$250.0684	$250.07	$250.05	$250.10
Purchase #7	$66.49	7.779%	$71.6623	$71.66	$71.65	$71.70
7 purchase totals =	$963.02		$1,047.1537	$1,047.16	$1,047.15	$1,047.20