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	$103.97	7.272%	$111.5307	$111.53	$111.55	$111.50
Purchase #2	$224.33	6.174%	$238.1801	$238.18	$238.20	$238.20
Purchase #3	$42.25	11.735%	$47.208	$47.21	$47.20	$47.20
Purchase #4	$144.93	12.393%	$162.8912	$162.89	$162.90	$162.90
Purchase #5	$141.48	13.686%	$160.843	$160.84	$160.85	$160.80
Purchase #6	$182.69	5.242%	$192.2666	$192.27	$192.25	$192.30
Purchase #7	$88.37	13.194%	$100.0295	$100.03	$100.05	$100.00
7 purchase totals =	$928.02		$1,012.9491	$1,012.95	$1,013.00	$1,012.90