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	$145.92	10.678%	$161.5013	$161.50	$161.50	$161.50
Purchase #2	$188.55	11.561%	$210.3483	$210.35	$210.35	$210.30
Purchase #3	$122.31	4.364%	$127.6476	$127.65	$127.65	$127.60
Purchase #4	$69.36	3.499%	$71.7869	$71.79	$71.80	$71.80
Purchase #5	$140.39	11.168%	$156.0688	$156.07	$156.05	$156.10
Purchase #6	$186.36	3.636%	$193.136	$193.14	$193.15	$193.10
Purchase #7	$154.66	6.340%	$164.4654	$164.47	$164.45	$164.50
7 purchase totals =	$1,007.55		$1,084.9543	$1,084.97	$1,084.95	$1,084.90