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	$191.57	5.765%	$202.614	$202.61	$202.60	$202.60
Purchase #2	$197.83	13.176%	$223.8961	$223.90	$223.90	$223.90
Purchase #3	$32.78	8.501%	$35.5666	$35.57	$35.55	$35.60
Purchase #4	$119.84	8.728%	$130.2996	$130.30	$130.30	$130.30
Purchase #5	$132.69	4.292%	$138.3851	$138.39	$138.40	$138.40
Purchase #6	$235.69	6.118%	$250.1095	$250.11	$250.10	$250.10
Purchase #7	$98.33	7.760%	$105.9604	$105.96	$105.95	$106.00
7 purchase totals =	$1,008.73		$1,086.8313	$1,086.84	$1,086.80	$1,086.90