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	$158.81	9.220%	$173.4523	$173.45	$173.45	$173.50
Purchase #2	$203.67	11.369%	$226.8252	$226.83	$226.85	$226.80
Purchase #3	$80.33	11.272%	$89.3848	$89.38	$89.40	$89.40
Purchase #4	$88.58	3.639%	$91.8034	$91.80	$91.80	$91.80
Purchase #5	$200.38	11.731%	$223.8866	$223.89	$223.90	$223.90
Purchase #6	$47.32	12.471%	$53.2213	$53.22	$53.20	$53.20
Purchase #7	$169.76	8.616%	$184.3865	$184.39	$184.40	$184.40
7 purchase totals =	$948.85		$1,042.9601	$1,042.96	$1,043.00	$1,043.00