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	$48.52	12.408%	$54.5404	$54.54	$54.55	$54.50
Purchase #2	$25.89	8.391%	$28.0624	$28.06	$28.05	$28.10
Purchase #3	$58.89	10.833%	$65.2696	$65.27	$65.25	$65.30
Purchase #4	$29.49	5.825%	$31.2078	$31.21	$31.20	$31.20
Purchase #5	$11.88	6.213%	$12.6181	$12.62	$12.60	$12.60
Purchase #6	$128.88	4.274%	$134.3883	$134.39	$134.40	$134.40
Purchase #7	$72.62	13.286%	$82.2683	$82.27	$82.25	$82.30
7 purchase totals =	$376.17		$408.3549	$408.36	$408.30	$408.40