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	$82.41	10.274%	$90.8768	$90.88	$90.90	$90.90
Purchase #2	$135.78	11.833%	$151.8468	$151.85	$151.85	$151.80
Purchase #3	$234.31	3.322%	$242.0938	$242.09	$242.10	$242.10
Purchase #4	$151.49	12.364%	$170.2202	$170.22	$170.20	$170.20
Purchase #5	$104.62	10.110%	$115.1971	$115.20	$115.20	$115.20
Purchase #6	$200.88	12.312%	$225.6123	$225.61	$225.60	$225.60
Purchase #7	$61.76	11.297%	$68.737	$68.74	$68.75	$68.70
7 purchase totals =	$971.25		$1,064.5840	$1,064.59	$1,064.60	$1,064.50