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	$161.78	12.559%	$182.098	$182.10	$182.10	$182.10
Purchase #2	$48.76	10.579%	$53.9183	$53.92	$53.90	$53.90
Purchase #3	$57.97	7.564%	$62.3549	$62.35	$62.35	$62.40
Purchase #4	$32.83	8.426%	$35.5963	$35.60	$35.60	$35.60
Purchase #5	$40.60	5.858%	$42.9783	$42.98	$43.00	$43.00
Purchase #6	$68.60	6.399%	$72.9897	$72.99	$73.00	$73.00
Purchase #7	$86.46	10.499%	$95.5374	$95.54	$95.55	$95.50
7 purchase totals =	$497.00		$545.4729	$545.48	$545.50	$545.50