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	$81.92	7.317%	$87.9141	$87.91	$87.90	$87.90
Purchase #2	$19.35	10.194%	$21.3225	$21.32	$21.30	$21.30
Purchase #3	$150.66	7.600%	$162.1102	$162.11	$162.10	$162.10
Purchase #4	$112.89	12.636%	$127.1548	$127.15	$127.15	$127.20
Purchase #5	$119.35	7.658%	$128.4898	$128.49	$128.50	$128.50
Purchase #6	$175.58	3.313%	$181.397	$181.40	$181.40	$181.40
Purchase #7	$245.87	9.679%	$269.6678	$269.67	$269.65	$269.70
7 purchase totals =	$905.62		$978.0562	$978.05	$978.00	$978.10