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	$86.99	6.789%	$92.8958	$92.90	$92.90	$92.90
Purchase #2	$48.91	9.649%	$53.6293	$53.63	$53.65	$53.60
Purchase #3	$211.33	3.107%	$217.896	$217.90	$217.90	$217.90
Purchase #4	$38.90	10.237%	$42.8822	$42.88	$42.90	$42.90
Purchase #5	$85.90	8.327%	$93.0529	$93.05	$93.05	$93.10
Purchase #6	$159.54	7.302%	$171.1896	$171.19	$171.20	$171.20
Purchase #7	$168.32	9.791%	$184.8002	$184.80	$184.80	$184.80
7 purchase totals =	$799.89		$856.3460	$856.35	$856.40	$856.40