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	$211.36	13.627%	$240.162	$240.16	$240.15	$240.20
Purchase #2	$52.30	13.409%	$59.3129	$59.31	$59.30	$59.30
Purchase #3	$211.47	5.134%	$222.3269	$222.33	$222.35	$222.30
Purchase #4	$187.89	9.323%	$205.407	$205.41	$205.40	$205.40
Purchase #5	$169.42	6.832%	$180.9948	$180.99	$181.00	$181.00
Purchase #6	$100.82	13.813%	$114.7463	$114.75	$114.75	$114.70
Purchase #7	$231.90	7.805%	$249.9998	$250.00	$250.00	$250.00
7 purchase totals =	$1,165.16		$1,272.9497	$1,272.95	$1,272.95	$1,272.90