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	$85.61	9.297%	$93.5692	$93.57	$93.55	$93.60
Purchase #2	$5.69	7.812%	$6.1345	$6.13	$6.15	$6.10
Purchase #3	$50.39	10.236%	$55.5479	$55.55	$55.55	$55.50
Purchase #4	$63.47	9.837%	$69.7135	$69.71	$69.70	$69.70
Purchase #5	$179.27	11.563%	$199.999	$200.00	$200.00	$200.00
Purchase #6	$30.63	9.124%	$33.4247	$33.42	$33.40	$33.40
Purchase #7	$196.95	6.237%	$209.2338	$209.23	$209.25	$209.20
7 purchase totals =	$612.01		$667.6226	$667.61	$667.60	$667.50