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	$188.79	3.868%	$196.0924	$196.09	$196.10	$196.10
Purchase #2	$6.98	12.391%	$7.8449	$7.84	$7.85	$7.80
Purchase #3	$238.63	8.675%	$259.3312	$259.33	$259.35	$259.30
Purchase #4	$222.41	6.581%	$237.0468	$237.05	$237.05	$237.00
Purchase #5	$91.79	3.414%	$94.9237	$94.92	$94.90	$94.90
Purchase #6	$173.39	10.431%	$191.4763	$191.48	$191.50	$191.50
Purchase #7	$33.38	5.331%	$35.1595	$35.16	$35.15	$35.20
7 purchase totals =	$955.37		$1,021.8748	$1,021.87	$1,021.90	$1,021.80