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	$117.65	7.634%	$126.6314	$126.63	$126.65	$126.60
Purchase #2	$213.31	7.403%	$229.1013	$229.10	$229.10	$229.10
Purchase #3	$91.42	10.437%	$100.9615	$100.96	$100.95	$101.00
Purchase #4	$120.91	8.228%	$130.8585	$130.86	$130.85	$130.90
Purchase #5	$145.31	6.260%	$154.4064	$154.41	$154.40	$154.40
Purchase #6	$37.78	6.679%	$40.3033	$40.30	$40.30	$40.30
Purchase #7	$31.57	6.280%	$33.5526	$33.55	$33.55	$33.60
7 purchase totals =	$757.95		$815.8150	$815.81	$815.80	$815.90