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	$136.37	5.665%	$144.0954	$144.10	$144.10	$144.10
Purchase #2	$162.43	5.455%	$171.2906	$171.29	$171.30	$171.30
Purchase #3	$137.60	12.858%	$155.2926	$155.29	$155.30	$155.30
Purchase #4	$90.58	7.728%	$97.58	$97.58	$97.60	$97.60
Purchase #5	$74.62	12.418%	$83.8863	$83.89	$83.90	$83.90
Purchase #6	$236.32	4.796%	$247.6539	$247.65	$247.65	$247.70
Purchase #7	$172.80	6.660%	$184.3085	$184.31	$184.30	$184.30
7 purchase totals =	$1,010.72		$1,084.1073	$1,084.11	$1,084.15	$1,084.20