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	$238.45	9.454%	$260.9931	$260.99	$261.00	$261.00
Purchase #2	$70.79	4.418%	$73.9175	$73.92	$73.90	$73.90
Purchase #3	$77.28	13.382%	$87.6216	$87.62	$87.60	$87.60
Purchase #4	$53.29	11.609%	$59.4764	$59.48	$59.50	$59.50
Purchase #5	$75.31	9.629%	$82.5616	$82.56	$82.55	$82.60
Purchase #6	$180.27	5.461%	$190.1145	$190.11	$190.10	$190.10
Purchase #7	$238.39	6.686%	$254.3288	$254.33	$254.35	$254.30
7 purchase totals =	$933.78		$1,009.0135	$1,009.01	$1,009.00	$1,009.00