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	$145.30	10.693%	$160.8369	$160.84	$160.85	$160.80
Purchase #2	$80.39	5.330%	$84.6748	$84.67	$84.65	$84.70
Purchase #3	$209.25	4.303%	$218.254	$218.25	$218.25	$218.30
Purchase #4	$141.47	13.206%	$160.1525	$160.15	$160.15	$160.20
Purchase #5	$84.56	5.650%	$89.3376	$89.34	$89.35	$89.30
Purchase #6	$108.90	6.794%	$116.2987	$116.30	$116.30	$116.30
Purchase #7	$161.69	11.647%	$180.522	$180.52	$180.50	$180.50
7 purchase totals =	$931.56		$1,010.0765	$1,010.07	$1,010.05	$1,010.10