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	$148.48	7.216%	$159.1943	$159.19	$159.20	$159.20
Purchase #2	$80.86	10.373%	$89.2476	$89.25	$89.25	$89.20
Purchase #3	$223.93	9.493%	$245.1877	$245.19	$245.20	$245.20
Purchase #4	$121.52	7.148%	$130.2062	$130.21	$130.20	$130.20
Purchase #5	$220.90	6.755%	$235.8218	$235.82	$235.80	$235.80
Purchase #6	$174.98	5.757%	$185.0536	$185.05	$185.05	$185.10
Purchase #7	$48.71	5.320%	$51.3014	$51.30	$51.30	$51.30
7 purchase totals =	$1,019.38		$1,096.0126	$1,096.01	$1,096.00	$1,096.00