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	$171.33	8.328%	$185.5984	$185.60	$185.60	$185.60
Purchase #2	$40.77	3.400%	$42.1562	$42.16	$42.15	$42.20
Purchase #3	$6.83	11.557%	$7.6193	$7.62	$7.60	$7.60
Purchase #4	$246.81	8.739%	$268.3787	$268.38	$268.40	$268.40
Purchase #5	$139.69	6.325%	$148.5254	$148.53	$148.55	$148.50
Purchase #6	$196.49	9.127%	$214.4236	$214.42	$214.40	$214.40
Purchase #7	$134.93	11.786%	$150.8328	$150.83	$150.85	$150.80
7 purchase totals =	$936.85		$1,017.5344	$1,017.54	$1,017.55	$1,017.50