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	$54.43	6.474%	$57.9538	$57.95	$57.95	$58.00
Purchase #2	$79.31	7.211%	$85.029	$85.03	$85.05	$85.00
Purchase #3	$239.50	12.760%	$270.0602	$270.06	$270.05	$270.10
Purchase #4	$192.56	10.546%	$212.8674	$212.87	$212.85	$212.90
Purchase #5	$169.36	10.165%	$186.5754	$186.58	$186.60	$186.60
Purchase #6	$46.58	13.592%	$52.9112	$52.91	$52.90	$52.90
Purchase #7	$97.92	13.732%	$111.3664	$111.37	$111.35	$111.40
7 purchase totals =	$879.66		$976.7634	$976.77	$976.75	$976.90