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	$247.58	6.601%	$263.9228	$263.92	$263.90	$263.90
Purchase #2	$79.45	12.703%	$89.5425	$89.54	$89.55	$89.50
Purchase #3	$32.33	11.180%	$35.9445	$35.94	$35.95	$35.90
Purchase #4	$228.25	13.243%	$258.4771	$258.48	$258.50	$258.50
Purchase #5	$245.57	12.518%	$276.3105	$276.31	$276.30	$276.30
Purchase #6	$216.31	6.478%	$230.3226	$230.32	$230.30	$230.30
Purchase #7	$185.28	3.389%	$191.5591	$191.56	$191.55	$191.60
7 purchase totals =	$1,234.77		$1,346.0791	$1,346.07	$1,346.05	$1,346.00