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	$218.46	5.241%	$229.9095	$229.91	$229.90	$229.90
Purchase #2	$109.46	4.677%	$114.5794	$114.58	$114.60	$114.60
Purchase #3	$138.57	10.297%	$152.8386	$152.84	$152.85	$152.80
Purchase #4	$178.40	11.723%	$199.3138	$199.31	$199.30	$199.30
Purchase #5	$68.53	9.419%	$74.9848	$74.98	$75.00	$75.00
Purchase #6	$220.96	10.858%	$244.9518	$244.95	$244.95	$245.00
Purchase #7	$37.85	13.272%	$42.8735	$42.87	$42.85	$42.90
7 purchase totals =	$972.23		$1,059.4514	$1,059.44	$1,059.45	$1,059.50