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	$30.35	11.825%	$33.9389	$33.94	$33.95	$33.90
Purchase #2	$72.26	13.696%	$82.1567	$82.16	$82.15	$82.20
Purchase #3	$232.77	4.330%	$242.8489	$242.85	$242.85	$242.80
Purchase #4	$62.57	12.781%	$70.5671	$70.57	$70.55	$70.60
Purchase #5	$159.90	13.771%	$181.9198	$181.92	$181.90	$181.90
Purchase #6	$154.41	8.720%	$167.8746	$167.87	$167.85	$167.90
Purchase #7	$235.43	4.626%	$246.321	$246.32	$246.30	$246.30
7 purchase totals =	$947.69		$1,025.6270	$1,025.63	$1,025.55	$1,025.60