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	$164.72	6.124%	$174.8075	$174.81	$174.80	$174.80
Purchase #2	$247.59	13.737%	$281.6014	$281.60	$281.60	$281.60
Purchase #3	$166.76	7.781%	$179.7356	$179.74	$179.75	$179.70
Purchase #4	$224.31	9.405%	$245.4064	$245.41	$245.40	$245.40
Purchase #5	$198.32	6.133%	$210.483	$210.48	$210.50	$210.50
Purchase #6	$149.92	6.389%	$159.4984	$159.50	$159.50	$159.50
Purchase #7	$90.82	6.211%	$96.4608	$96.46	$96.45	$96.50
7 purchase totals =	$1,242.44		$1,347.9931	$1,348.00	$1,348.00	$1,348.00