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	$105.29	9.234%	$115.0125	$115.01	$115.00	$115.00
Purchase #2	$65.71	11.778%	$73.4493	$73.45	$73.45	$73.40
Purchase #3	$33.54	11.322%	$37.3374	$37.34	$37.35	$37.30
Purchase #4	$136.79	10.564%	$151.2405	$151.24	$151.25	$151.20
Purchase #5	$239.51	6.267%	$254.5201	$254.52	$254.50	$254.50
Purchase #6	$222.87	9.744%	$244.5865	$244.59	$244.60	$244.60
Purchase #7	$131.94	13.853%	$150.2176	$150.22	$150.20	$150.20
7 purchase totals =	$935.65		$1,026.3639	$1,026.37	$1,026.35	$1,026.20