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	$245.43	3.253%	$253.4138	$253.41	$253.40	$253.40
Purchase #2	$247.39	4.791%	$259.2425	$259.24	$259.25	$259.20
Purchase #3	$136.60	4.647%	$142.9478	$142.95	$142.95	$142.90
Purchase #4	$162.90	13.154%	$184.3279	$184.33	$184.35	$184.30
Purchase #5	$146.81	13.294%	$166.3269	$166.33	$166.35	$166.30
Purchase #6	$91.84	9.415%	$100.4867	$100.49	$100.50	$100.50
Purchase #7	$171.67	5.408%	$180.9539	$180.95	$180.95	$181.00
7 purchase totals =	$1,202.64		$1,287.6995	$1,287.70	$1,287.75	$1,287.60