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	$197.40	7.199%	$211.6108	$211.61	$211.60	$211.60
Purchase #2	$132.41	3.718%	$137.333	$137.33	$137.35	$137.30
Purchase #3	$40.42	6.319%	$42.9741	$42.97	$42.95	$43.00
Purchase #4	$137.69	6.279%	$146.3356	$146.34	$146.35	$146.30
Purchase #5	$246.94	6.293%	$262.4799	$262.48	$262.50	$262.50
Purchase #6	$178.38	3.847%	$185.2423	$185.24	$185.25	$185.20
Purchase #7	$32.74	8.535%	$35.5344	$35.53	$35.55	$35.50
7 purchase totals =	$965.98		$1,021.5101	$1,021.50	$1,021.55	$1,021.40