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	$76.37	4.280%	$79.6386	$79.64	$79.65	$79.60
Purchase #2	$32.27	4.167%	$33.6147	$33.61	$33.60	$33.60
Purchase #3	$235.92	13.569%	$267.932	$267.93	$267.95	$267.90
Purchase #4	$96.89	8.360%	$104.99	$104.99	$105.00	$105.00
Purchase #5	$57.46	13.661%	$65.3096	$65.31	$65.30	$65.30
Purchase #6	$158.69	13.807%	$180.6003	$180.60	$180.60	$180.60
Purchase #7	$67.79	4.405%	$70.7761	$70.78	$70.80	$70.80
7 purchase totals =	$725.39		$802.8613	$802.86	$802.90	$802.80