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	$206.54	7.488%	$222.0057	$222.01	$222.00	$222.00
Purchase #2	$43.82	9.236%	$47.8672	$47.87	$47.85	$47.90
Purchase #3	$68.35	4.446%	$71.3888	$71.39	$71.40	$71.40
Purchase #4	$27.87	4.666%	$29.1704	$29.17	$29.15	$29.20
Purchase #5	$209.68	9.243%	$229.0607	$229.06	$229.05	$229.10
Purchase #6	$176.72	11.375%	$196.8219	$196.82	$196.80	$196.80
Purchase #7	$163.65	5.662%	$172.9159	$172.92	$172.90	$172.90
7 purchase totals =	$896.63		$969.2306	$969.24	$969.15	$969.30