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	$67.50	7.350%	$72.4613	$72.46	$72.45	$72.50
Purchase #2	$117.39	9.431%	$128.4611	$128.46	$128.45	$128.50
Purchase #3	$67.36	3.362%	$69.6246	$69.62	$69.60	$69.60
Purchase #4	$200.89	10.671%	$222.327	$222.33	$222.35	$222.30
Purchase #5	$122.44	10.798%	$135.6611	$135.66	$135.65	$135.70
Purchase #6	$180.25	4.498%	$188.3576	$188.36	$188.35	$188.40
Purchase #7	$61.78	6.686%	$65.9106	$65.91	$65.90	$65.90
7 purchase totals =	$817.61		$882.8033	$882.80	$882.75	$882.90