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	$145.63	4.304%	$151.8979	$151.90	$151.90	$151.90
Purchase #2	$63.75	3.373%	$65.9003	$65.90	$65.90	$65.90
Purchase #3	$238.82	10.835%	$264.6961	$264.70	$264.70	$264.70
Purchase #4	$31.74	12.212%	$35.6161	$35.62	$35.60	$35.60
Purchase #5	$220.40	12.868%	$248.7611	$248.76	$248.75	$248.80
Purchase #6	$178.47	9.860%	$196.0671	$196.07	$196.05	$196.10
Purchase #7	$59.47	4.561%	$62.1824	$62.18	$62.20	$62.20
7 purchase totals =	$938.28		$1,025.1210	$1,025.13	$1,025.10	$1,025.20