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	$175.96	4.599%	$184.0524	$184.05	$184.05	$184.10
Purchase #2	$186.71	4.226%	$194.6004	$194.60	$194.60	$194.60
Purchase #3	$55.56	12.483%	$62.4956	$62.50	$62.50	$62.50
Purchase #4	$29.91	8.564%	$32.4715	$32.47	$32.45	$32.50
Purchase #5	$30.57	4.160%	$31.8417	$31.84	$31.85	$31.80
Purchase #6	$65.61	7.437%	$70.4894	$70.49	$70.50	$70.50
Purchase #7	$92.62	7.786%	$99.8314	$99.83	$99.85	$99.80
7 purchase totals =	$636.94		$675.7824	$675.78	$675.80	$675.80