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	$152.71	6.458%	$162.572	$162.57	$162.55	$162.60
Purchase #2	$174.75	7.831%	$188.4347	$188.43	$188.45	$188.40
Purchase #3	$141.58	13.617%	$160.8589	$160.86	$160.85	$160.90
Purchase #4	$225.66	10.346%	$249.0068	$249.01	$249.00	$249.00
Purchase #5	$130.87	6.871%	$139.8621	$139.86	$139.85	$139.90
Purchase #6	$33.75	4.220%	$35.1743	$35.17	$35.15	$35.20
Purchase #7	$160.93	7.268%	$172.6264	$172.63	$172.65	$172.60
7 purchase totals =	$1,020.25		$1,108.5352	$1,108.53	$1,108.50	$1,108.60