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	$30.50	8.507%	$33.0946	$33.09	$33.10	$33.10
Purchase #2	$194.78	8.769%	$211.8603	$211.86	$211.85	$211.90
Purchase #3	$37.82	7.817%	$40.7764	$40.78	$40.80	$40.80
Purchase #4	$121.85	12.172%	$136.6816	$136.68	$136.70	$136.70
Purchase #5	$79.91	12.168%	$89.6334	$89.63	$89.65	$89.60
Purchase #6	$189.90	4.445%	$198.3411	$198.34	$198.35	$198.30
Purchase #7	$149.53	11.142%	$166.1906	$166.19	$166.20	$166.20
7 purchase totals =	$804.29		$876.5780	$876.57	$876.65	$876.60