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	$135.84	4.168%	$141.5018	$141.50	$141.50	$141.50
Purchase #2	$205.37	4.497%	$214.6055	$214.61	$214.60	$214.60
Purchase #3	$26.25	8.839%	$28.5702	$28.57	$28.55	$28.60
Purchase #4	$27.31	4.703%	$28.5944	$28.59	$28.60	$28.60
Purchase #5	$41.90	8.148%	$45.314	$45.31	$45.30	$45.30
Purchase #6	$67.50	7.121%	$72.3067	$72.31	$72.30	$72.30
Purchase #7	$150.53	9.773%	$165.2413	$165.24	$165.25	$165.20
7 purchase totals =	$654.70		$696.1339	$696.13	$696.10	$696.10