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	$99.71	8.415%	$108.1006	$108.10	$108.10	$108.10
Purchase #2	$149.79	12.796%	$168.9571	$168.96	$168.95	$169.00
Purchase #3	$100.64	4.516%	$105.1849	$105.18	$105.20	$105.20
Purchase #4	$219.44	12.110%	$246.0142	$246.01	$246.00	$246.00
Purchase #5	$181.77	7.861%	$196.0589	$196.06	$196.05	$196.10
Purchase #6	$237.34	13.165%	$268.5858	$268.59	$268.60	$268.60
Purchase #7	$173.86	13.154%	$196.7295	$196.73	$196.75	$196.70
7 purchase totals =	$1,162.55		$1,289.6310	$1,289.63	$1,289.65	$1,289.70