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	$247.96	7.836%	$267.3901	$267.39	$267.40	$267.40
Purchase #2	$119.34	5.647%	$126.0791	$126.08	$126.10	$126.10
Purchase #3	$228.59	7.242%	$245.1445	$245.14	$245.15	$245.10
Purchase #4	$47.32	10.565%	$52.3194	$52.32	$52.30	$52.30
Purchase #5	$243.84	6.162%	$258.8654	$258.87	$258.85	$258.90
Purchase #6	$59.55	5.604%	$62.8872	$62.89	$62.90	$62.90
Purchase #7	$138.86	9.187%	$151.6171	$151.62	$151.60	$151.60
7 purchase totals =	$1,085.46		$1,164.3028	$1,164.31	$1,164.30	$1,164.30