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	$80.77	11.129%	$89.7589	$89.76	$89.75	$89.80
Purchase #2	$74.35	11.173%	$82.6571	$82.66	$82.65	$82.70
Purchase #3	$85.71	8.788%	$93.2422	$93.24	$93.25	$93.20
Purchase #4	$81.96	8.467%	$88.8996	$88.90	$88.90	$88.90
Purchase #5	$56.51	3.357%	$58.407	$58.41	$58.40	$58.40
Purchase #6	$152.28	13.797%	$173.2901	$173.29	$173.30	$173.30
Purchase #7	$112.89	13.164%	$127.7508	$127.75	$127.75	$127.80
7 purchase totals =	$644.47		$714.0057	$714.01	$714.00	$714.10