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	$89.65	6.567%	$95.5373	$95.54	$95.55	$95.50
Purchase #2	$241.38	13.175%	$273.1818	$273.18	$273.20	$273.20
Purchase #3	$163.84	6.401%	$174.3274	$174.33	$174.35	$174.30
Purchase #4	$23.71	4.873%	$24.8654	$24.87	$24.85	$24.90
Purchase #5	$233.88	10.623%	$258.7251	$258.73	$258.75	$258.70
Purchase #6	$65.61	10.608%	$72.5699	$72.57	$72.55	$72.60
Purchase #7	$107.91	11.761%	$120.6013	$120.60	$120.60	$120.60
7 purchase totals =	$925.98		$1,019.8082	$1,019.82	$1,019.85	$1,019.80