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	$69.35	3.651%	$71.882	$71.88	$71.90	$71.90
Purchase #2	$70.69	13.780%	$80.4311	$80.43	$80.45	$80.40
Purchase #3	$88.27	12.520%	$99.3214	$99.32	$99.30	$99.30
Purchase #4	$6.93	7.390%	$7.4421	$7.44	$7.45	$7.40
Purchase #5	$241.86	8.431%	$262.2512	$262.25	$262.25	$262.30
Purchase #6	$144.58	4.658%	$151.3145	$151.31	$151.30	$151.30
Purchase #7	$247.97	8.416%	$268.8392	$268.84	$268.85	$268.80
7 purchase totals =	$869.65		$941.4815	$941.47	$941.50	$941.40