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	$124.54	4.839%	$130.5665	$130.57	$130.55	$130.60
Purchase #2	$155.28	7.603%	$167.0859	$167.09	$167.10	$167.10
Purchase #3	$212.95	10.498%	$235.3055	$235.31	$235.30	$235.30
Purchase #4	$114.56	7.639%	$123.3112	$123.31	$123.30	$123.30
Purchase #5	$63.56	7.285%	$68.1903	$68.19	$68.20	$68.20
Purchase #6	$184.26	4.533%	$192.6125	$192.61	$192.60	$192.60
Purchase #7	$93.73	6.744%	$100.0512	$100.05	$100.05	$100.10
7 purchase totals =	$948.88		$1,017.1231	$1,017.13	$1,017.10	$1,017.20