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	$31.28	4.717%	$32.7555	$32.76	$32.75	$32.80
Purchase #2	$211.61	10.540%	$233.9137	$233.91	$233.90	$233.90
Purchase #3	$39.42	3.608%	$40.8423	$40.84	$40.85	$40.80
Purchase #4	$84.85	11.558%	$94.657	$94.66	$94.65	$94.70
Purchase #5	$232.66	5.146%	$244.6327	$244.63	$244.65	$244.60
Purchase #6	$224.45	13.462%	$254.6655	$254.67	$254.65	$254.70
Purchase #7	$191.36	9.831%	$210.1726	$210.17	$210.15	$210.20
7 purchase totals =	$1,015.63		$1,111.6393	$1,111.64	$1,111.60	$1,111.70