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	$185.47	6.874%	$198.2192	$198.22	$198.20	$198.20
Purchase #2	$70.73	13.628%	$80.3691	$80.37	$80.35	$80.40
Purchase #3	$31.26	13.759%	$35.5611	$35.56	$35.55	$35.60
Purchase #4	$189.76	7.740%	$204.4474	$204.45	$204.45	$204.40
Purchase #5	$89.46	11.392%	$99.6513	$99.65	$99.65	$99.70
Purchase #6	$201.98	10.340%	$222.8647	$222.86	$222.85	$222.90
Purchase #7	$226.87	6.159%	$240.8429	$240.84	$240.85	$240.80
7 purchase totals =	$995.53		$1,081.9557	$1,081.95	$1,081.90	$1,082.00