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	$234.53	4.238%	$244.4694	$244.47	$244.45	$244.50
Purchase #2	$216.82	4.719%	$227.0517	$227.05	$227.05	$227.10
Purchase #3	$120.61	8.240%	$130.5483	$130.55	$130.55	$130.50
Purchase #4	$102.64	6.618%	$109.4327	$109.43	$109.45	$109.40
Purchase #5	$156.51	3.549%	$162.0645	$162.06	$162.05	$162.10
Purchase #6	$28.78	7.774%	$31.0174	$31.02	$31.00	$31.00
Purchase #7	$184.32	5.667%	$194.7654	$194.77	$194.75	$194.80
7 purchase totals =	$1,044.21		$1,099.3494	$1,099.35	$1,099.30	$1,099.40