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	$188.62	12.496%	$212.19	$212.19	$212.20	$212.20
Purchase #2	$124.57	5.860%	$131.8698	$131.87	$131.85	$131.90
Purchase #3	$191.54	7.452%	$205.8136	$205.81	$205.80	$205.80
Purchase #4	$35.55	6.553%	$37.8796	$37.88	$37.90	$37.90
Purchase #5	$203.28	11.476%	$226.6084	$226.61	$226.60	$226.60
Purchase #6	$240.49	11.791%	$268.8462	$268.85	$268.85	$268.80
Purchase #7	$40.38	12.685%	$45.5022	$45.50	$45.50	$45.50
7 purchase totals =	$1,024.43		$1,128.7098	$1,128.71	$1,128.70	$1,128.70