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	$136.34	12.478%	$153.3525	$153.35	$153.35	$153.40
Purchase #2	$240.51	8.663%	$261.3454	$261.35	$261.35	$261.30
Purchase #3	$144.35	6.215%	$153.3214	$153.32	$153.30	$153.30
Purchase #4	$104.75	7.108%	$112.1956	$112.20	$112.20	$112.20
Purchase #5	$167.91	13.364%	$190.3495	$190.35	$190.35	$190.30
Purchase #6	$24.91	12.428%	$28.0058	$28.01	$28.00	$28.00
Purchase #7	$155.74	7.804%	$167.8939	$167.89	$167.90	$167.90
7 purchase totals =	$974.51		$1,066.4641	$1,066.47	$1,066.45	$1,066.40