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	$71.97	7.492%	$77.362	$77.36	$77.35	$77.40
Purchase #2	$154.38	13.123%	$174.6393	$174.64	$174.65	$174.60
Purchase #3	$37.83	10.772%	$41.905	$41.91	$41.90	$41.90
Purchase #4	$83.93	12.480%	$94.4045	$94.40	$94.40	$94.40
Purchase #5	$42.68	11.112%	$47.4226	$47.42	$47.40	$47.40
Purchase #6	$219.81	7.756%	$236.8585	$236.86	$236.85	$236.90
Purchase #7	$227.29	6.164%	$241.3002	$241.30	$241.30	$241.30
7 purchase totals =	$837.89		$913.8921	$913.89	$913.85	$913.90