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	$103.76	7.755%	$111.8066	$111.81	$111.80	$111.80
Purchase #2	$103.46	7.819%	$111.5495	$111.55	$111.55	$111.50
Purchase #3	$226.30	7.269%	$242.7497	$242.75	$242.75	$242.70
Purchase #4	$14.25	7.575%	$15.3294	$15.33	$15.35	$15.30
Purchase #5	$174.31	13.233%	$197.3764	$197.38	$197.40	$197.40
Purchase #6	$32.36	9.169%	$35.3271	$35.33	$35.35	$35.30
Purchase #7	$130.77	11.296%	$145.5418	$145.54	$145.55	$145.50
7 purchase totals =	$785.21		$859.6805	$859.69	$859.75	$859.50