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	$183.54	7.205%	$196.7641	$196.76	$196.75	$196.80
Purchase #2	$79.57	12.600%	$89.5958	$89.60	$89.60	$89.60
Purchase #3	$133.69	4.569%	$139.7983	$139.80	$139.80	$139.80
Purchase #4	$195.45	5.564%	$206.3248	$206.32	$206.30	$206.30
Purchase #5	$147.71	9.299%	$161.4456	$161.45	$161.45	$161.40
Purchase #6	$19.55	5.703%	$20.6649	$20.66	$20.65	$20.70
Purchase #7	$182.42	12.230%	$204.73	$204.73	$204.75	$204.70
7 purchase totals =	$941.93		$1,019.3235	$1,019.32	$1,019.30	$1,019.30