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	$69.48	11.422%	$77.416	$77.42	$77.40	$77.40
Purchase #2	$55.51	10.499%	$61.338	$61.34	$61.35	$61.30
Purchase #3	$17.63	12.780%	$19.8831	$19.88	$19.90	$19.90
Purchase #4	$93.38	11.470%	$104.0907	$104.09	$104.10	$104.10
Purchase #5	$187.28	5.108%	$196.8463	$196.85	$196.85	$196.80
Purchase #6	$159.78	12.358%	$179.5256	$179.53	$179.55	$179.50
Purchase #7	$35.26	8.412%	$38.2261	$38.23	$38.25	$38.20
7 purchase totals =	$618.32		$677.3258	$677.34	$677.40	$677.20