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	$102.76	3.268%	$106.1182	$106.12	$106.10	$106.10
Purchase #2	$92.52	9.292%	$101.117	$101.12	$101.10	$101.10
Purchase #3	$149.91	5.614%	$158.3259	$158.33	$158.35	$158.30
Purchase #4	$151.82	10.836%	$168.2712	$168.27	$168.25	$168.30
Purchase #5	$94.35	6.556%	$100.5356	$100.54	$100.55	$100.50
Purchase #6	$137.39	6.132%	$145.8148	$145.81	$145.80	$145.80
Purchase #7	$23.90	10.676%	$26.4516	$26.45	$26.45	$26.50
7 purchase totals =	$752.65		$806.6343	$806.64	$806.60	$806.60