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	$65.39	10.337%	$72.1494	$72.15	$72.15	$72.10
Purchase #2	$231.53	7.511%	$248.9202	$248.92	$248.90	$248.90
Purchase #3	$31.50	4.849%	$33.0274	$33.03	$33.05	$33.00
Purchase #4	$93.72	3.456%	$96.959	$96.96	$96.95	$97.00
Purchase #5	$105.64	6.303%	$112.2985	$112.30	$112.30	$112.30
Purchase #6	$244.39	10.143%	$269.1785	$269.18	$269.20	$269.20
Purchase #7	$20.82	3.538%	$21.5566	$21.56	$21.55	$21.60
7 purchase totals =	$792.99		$854.0896	$854.10	$854.10	$854.10