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	$182.36	4.205%	$190.0282	$190.03	$190.05	$190.00
Purchase #2	$198.97	8.595%	$216.0715	$216.07	$216.05	$216.10
Purchase #3	$40.34	13.629%	$45.8379	$45.84	$45.85	$45.80
Purchase #4	$62.64	3.633%	$64.9157	$64.92	$64.90	$64.90
Purchase #5	$228.81	7.360%	$245.6504	$245.65	$245.65	$245.70
Purchase #6	$200.74	10.235%	$221.2857	$221.29	$221.30	$221.30
Purchase #7	$111.87	13.813%	$127.3226	$127.32	$127.30	$127.30
7 purchase totals =	$1,025.73		$1,111.1120	$1,111.12	$1,111.10	$1,111.10