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	$148.72	7.430%	$159.7699	$159.77	$159.75	$159.80
Purchase #2	$78.62	5.687%	$83.0911	$83.09	$83.10	$83.10
Purchase #3	$143.80	4.860%	$150.7887	$150.79	$150.80	$150.80
Purchase #4	$236.98	9.363%	$259.1684	$259.17	$259.15	$259.20
Purchase #5	$159.66	12.122%	$179.014	$179.01	$179.00	$179.00
Purchase #6	$109.97	12.199%	$123.3852	$123.39	$123.40	$123.40
Purchase #7	$176.30	3.181%	$181.9081	$181.91	$181.90	$181.90
7 purchase totals =	$1,054.05		$1,137.1254	$1,137.13	$1,137.10	$1,137.20