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	$150.31	13.465%	$170.5492	$170.55	$170.55	$170.50
Purchase #2	$87.38	7.423%	$93.8662	$93.87	$93.85	$93.90
Purchase #3	$166.50	7.599%	$179.1523	$179.15	$179.15	$179.20
Purchase #4	$162.60	5.362%	$171.3186	$171.32	$171.30	$171.30
Purchase #5	$98.67	4.147%	$102.7618	$102.76	$102.75	$102.80
Purchase #6	$227.25	7.435%	$244.146	$244.15	$244.15	$244.10
Purchase #7	$94.31	6.717%	$100.6448	$100.64	$100.65	$100.60
7 purchase totals =	$987.02		$1,062.4389	$1,062.44	$1,062.40	$1,062.40