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	$114.37	7.825%	$123.3195	$123.32	$123.30	$123.30
Purchase #2	$245.57	12.113%	$275.3159	$275.32	$275.30	$275.30
Purchase #3	$128.38	7.679%	$138.2383	$138.24	$138.25	$138.20
Purchase #4	$122.78	9.367%	$134.2808	$134.28	$134.30	$134.30
Purchase #5	$105.36	8.792%	$114.6233	$114.62	$114.60	$114.60
Purchase #6	$150.53	9.219%	$164.4074	$164.41	$164.40	$164.40
Purchase #7	$151.65	8.613%	$164.7116	$164.71	$164.70	$164.70
7 purchase totals =	$1,018.64		$1,114.8968	$1,114.90	$1,114.85	$1,114.80