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	$216.63	11.646%	$241.8587	$241.86	$241.85	$241.90
Purchase #2	$185.41	3.317%	$191.56	$191.56	$191.55	$191.60
Purchase #3	$44.39	8.274%	$48.0628	$48.06	$48.05	$48.10
Purchase #4	$47.42	6.332%	$50.4226	$50.42	$50.40	$50.40
Purchase #5	$104.27	4.792%	$109.2666	$109.27	$109.25	$109.30
Purchase #6	$188.67	3.201%	$194.7093	$194.71	$194.70	$194.70
Purchase #7	$105.63	6.247%	$112.2287	$112.23	$112.25	$112.20
7 purchase totals =	$892.42		$948.1087	$948.11	$948.05	$948.20