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	$100.92	13.839%	$114.8863	$114.89	$114.90	$114.90
Purchase #2	$236.62	3.174%	$244.1303	$244.13	$244.15	$244.10
Purchase #3	$65.92	6.296%	$70.0703	$70.07	$70.05	$70.10
Purchase #4	$98.59	3.597%	$102.1363	$102.14	$102.15	$102.10
Purchase #5	$223.91	3.120%	$230.896	$230.90	$230.90	$230.90
Purchase #6	$82.36	3.230%	$85.0202	$85.02	$85.00	$85.00
Purchase #7	$211.88	11.789%	$236.8585	$236.86	$236.85	$236.90
7 purchase totals =	$1,020.20		$1,083.9979	$1,084.01	$1,084.00	$1,084.00