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	$116.48	5.437%	$122.813	$122.81	$122.80	$122.80
Purchase #2	$152.72	6.114%	$162.0573	$162.06	$162.05	$162.10
Purchase #3	$205.72	6.250%	$218.5775	$218.58	$218.60	$218.60
Purchase #4	$98.91	9.641%	$108.4459	$108.45	$108.45	$108.40
Purchase #5	$92.81	11.797%	$103.7588	$103.76	$103.75	$103.80
Purchase #6	$30.80	4.828%	$32.287	$32.29	$32.30	$32.30
Purchase #7	$240.88	12.601%	$271.2333	$271.23	$271.25	$271.20
7 purchase totals =	$938.32		$1,019.1728	$1,019.18	$1,019.20	$1,019.20