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	$234.69	4.663%	$245.6336	$245.63	$245.65	$245.60
Purchase #2	$154.96	9.483%	$169.6549	$169.65	$169.65	$169.70
Purchase #3	$13.71	10.227%	$15.1121	$15.11	$15.10	$15.10
Purchase #4	$73.28	7.442%	$78.7335	$78.73	$78.75	$78.70
Purchase #5	$100.46	11.107%	$111.6181	$111.62	$111.60	$111.60
Purchase #6	$34.98	11.542%	$39.0174	$39.02	$39.00	$39.00
Purchase #7	$245.50	13.384%	$278.3577	$278.36	$278.35	$278.40
7 purchase totals =	$857.58		$938.1273	$938.12	$938.10	$938.10