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	$80.57	5.428%	$84.9433	$84.94	$84.95	$84.90
Purchase #2	$227.75	12.536%	$256.3007	$256.30	$256.30	$256.30
Purchase #3	$141.77	6.368%	$150.7979	$150.80	$150.80	$150.80
Purchase #4	$64.76	4.229%	$67.4987	$67.50	$67.50	$67.50
Purchase #5	$70.58	11.312%	$78.564	$78.56	$78.55	$78.60
Purchase #6	$130.52	3.489%	$135.0738	$135.07	$135.05	$135.10
Purchase #7	$220.85	3.372%	$228.2971	$228.30	$228.30	$228.30
7 purchase totals =	$936.80		$1,001.4755	$1,001.47	$1,001.45	$1,001.50