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	$203.81	6.286%	$216.6215	$216.62	$216.60	$216.60
Purchase #2	$70.44	3.684%	$73.035	$73.04	$73.05	$73.00
Purchase #3	$89.91	12.794%	$101.4131	$101.41	$101.40	$101.40
Purchase #4	$221.40	5.511%	$233.6014	$233.60	$233.60	$233.60
Purchase #5	$238.43	6.591%	$254.1449	$254.14	$254.15	$254.10
Purchase #6	$91.82	12.817%	$103.5886	$103.59	$103.60	$103.60
Purchase #7	$101.52	12.220%	$113.9257	$113.93	$113.95	$113.90
7 purchase totals =	$1,017.33		$1,096.3302	$1,096.33	$1,096.35	$1,096.20