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	$141.27	11.299%	$157.2321	$157.23	$157.25	$157.20
Purchase #2	$82.92	3.267%	$85.629	$85.63	$85.65	$85.60
Purchase #3	$228.27	5.559%	$240.9595	$240.96	$240.95	$241.00
Purchase #4	$96.42	6.349%	$102.5417	$102.54	$102.55	$102.50
Purchase #5	$101.87	3.766%	$105.7064	$105.71	$105.70	$105.70
Purchase #6	$195.54	4.132%	$203.6197	$203.62	$203.60	$203.60
Purchase #7	$238.73	6.662%	$254.6342	$254.63	$254.65	$254.60
7 purchase totals =	$1,085.02		$1,150.3226	$1,150.32	$1,150.35	$1,150.20