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	$97.54	5.712%	$103.1115	$103.11	$103.10	$103.10
Purchase #2	$21.49	13.669%	$24.4275	$24.43	$24.45	$24.40
Purchase #3	$31.31	12.789%	$35.3142	$35.31	$35.30	$35.30
Purchase #4	$210.49	8.276%	$227.9102	$227.91	$227.90	$227.90
Purchase #5	$97.37	3.483%	$100.7614	$100.76	$100.75	$100.80
Purchase #6	$145.91	7.258%	$156.5001	$156.50	$156.50	$156.50
Purchase #7	$188.40	6.530%	$200.7025	$200.70	$200.70	$200.70
7 purchase totals =	$792.51		$848.7274	$848.72	$848.70	$848.70