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	$229.56	5.524%	$242.2409	$242.24	$242.25	$242.20
Purchase #2	$98.54	6.641%	$105.084	$105.08	$105.10	$105.10
Purchase #3	$198.57	12.732%	$223.8519	$223.85	$223.85	$223.90
Purchase #4	$13.55	7.831%	$14.6111	$14.61	$14.60	$14.60
Purchase #5	$11.96	9.799%	$13.132	$13.13	$13.15	$13.10
Purchase #6	$17.42	13.741%	$19.8137	$19.81	$19.80	$19.80
Purchase #7	$79.90	6.795%	$85.3292	$85.33	$85.35	$85.30
7 purchase totals =	$649.50		$704.0628	$704.05	$704.10	$704.00