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	$198.86	6.491%	$211.768	$211.77	$211.75	$211.80
Purchase #2	$42.94	12.556%	$48.3315	$48.33	$48.35	$48.30
Purchase #3	$113.69	8.774%	$123.6652	$123.67	$123.65	$123.70
Purchase #4	$178.51	5.229%	$187.8443	$187.84	$187.85	$187.80
Purchase #5	$102.71	6.278%	$109.1581	$109.16	$109.15	$109.20
Purchase #6	$237.37	10.858%	$263.1436	$263.14	$263.15	$263.10
Purchase #7	$50.56	11.279%	$56.2627	$56.26	$56.25	$56.30
7 purchase totals =	$924.64		$1,000.1734	$1,000.17	$1,000.15	$1,000.20