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	$228.57	9.585%	$250.4784	$250.48	$250.50	$250.50
Purchase #2	$223.32	3.382%	$230.8727	$230.87	$230.85	$230.90
Purchase #3	$26.27	9.226%	$28.6937	$28.69	$28.70	$28.70
Purchase #4	$91.41	9.663%	$100.2429	$100.24	$100.25	$100.20
Purchase #5	$158.38	3.789%	$164.381	$164.38	$164.40	$164.40
Purchase #6	$182.83	7.768%	$197.0322	$197.03	$197.05	$197.00
Purchase #7	$46.48	9.282%	$50.7943	$50.79	$50.80	$50.80
7 purchase totals =	$957.26		$1,022.4952	$1,022.48	$1,022.55	$1,022.50