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	$191.70	9.781%	$210.4502	$210.45	$210.45	$210.50
Purchase #2	$139.66	11.590%	$155.8466	$155.85	$155.85	$155.80
Purchase #3	$120.64	5.705%	$127.5225	$127.52	$127.50	$127.50
Purchase #4	$95.77	7.856%	$103.2937	$103.29	$103.30	$103.30
Purchase #5	$207.38	12.819%	$233.964	$233.96	$233.95	$234.00
Purchase #6	$135.92	3.768%	$141.0415	$141.04	$141.05	$141.00
Purchase #7	$170.87	3.419%	$176.712	$176.71	$176.70	$176.70
7 purchase totals =	$1,061.94		$1,148.8305	$1,148.82	$1,148.80	$1,148.80