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	$201.67	13.124%	$228.1372	$228.14	$228.15	$228.10
Purchase #2	$204.63	3.248%	$211.2764	$211.28	$211.30	$211.30
Purchase #3	$42.37	7.730%	$45.6452	$45.65	$45.65	$45.60
Purchase #4	$49.69	6.796%	$53.0669	$53.07	$53.05	$53.10
Purchase #5	$98.62	6.472%	$105.0027	$105.00	$105.00	$105.00
Purchase #6	$146.73	6.635%	$156.4655	$156.47	$156.45	$156.50
Purchase #7	$55.34	6.675%	$59.0339	$59.03	$59.05	$59.00
7 purchase totals =	$799.05		$858.6278	$858.64	$858.65	$858.60