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	$57.26	10.240%	$63.1234	$63.12	$63.10	$63.10
Purchase #2	$81.80	4.478%	$85.463	$85.46	$85.45	$85.50
Purchase #3	$12.41	9.688%	$13.6123	$13.61	$13.60	$13.60
Purchase #4	$229.52	3.870%	$238.4024	$238.40	$238.40	$238.40
Purchase #5	$162.92	13.677%	$185.2026	$185.20	$185.20	$185.20
Purchase #6	$142.57	7.725%	$153.5835	$153.58	$153.60	$153.60
Purchase #7	$240.58	13.550%	$273.1786	$273.18	$273.20	$273.20
7 purchase totals =	$927.06		$1,012.5658	$1,012.55	$1,012.55	$1,012.60