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	$202.36	10.647%	$223.9053	$223.91	$223.90	$223.90
Purchase #2	$87.89	7.316%	$94.32	$94.32	$94.30	$94.30
Purchase #3	$232.93	7.460%	$250.3066	$250.31	$250.30	$250.30
Purchase #4	$231.63	13.501%	$262.9024	$262.90	$262.90	$262.90
Purchase #5	$190.48	11.699%	$212.7643	$212.76	$212.75	$212.80
Purchase #6	$78.56	5.752%	$83.0788	$83.08	$83.10	$83.10
Purchase #7	$52.71	13.604%	$59.8807	$59.88	$59.90	$59.90
7 purchase totals =	$1,076.56		$1,187.1581	$1,187.16	$1,187.15	$1,187.20