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	$185.75	5.633%	$196.2133	$196.21	$196.20	$196.20
Purchase #2	$229.85	4.118%	$239.3152	$239.32	$239.30	$239.30
Purchase #3	$115.30	13.411%	$130.7629	$130.76	$130.75	$130.80
Purchase #4	$33.94	11.541%	$37.857	$37.86	$37.85	$37.90
Purchase #5	$18.35	5.644%	$19.3857	$19.39	$19.40	$19.40
Purchase #6	$24.75	12.264%	$27.7853	$27.79	$27.80	$27.80
Purchase #7	$49.25	10.356%	$54.3503	$54.35	$54.35	$54.40
7 purchase totals =	$657.19		$705.6697	$705.68	$705.65	$705.80