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	$166.43	4.562%	$174.0225	$174.02	$174.00	$174.00
Purchase #2	$170.97	12.662%	$192.6182	$192.62	$192.60	$192.60
Purchase #3	$65.73	9.341%	$71.8698	$71.87	$71.85	$71.90
Purchase #4	$198.54	6.808%	$212.0566	$212.06	$212.05	$212.10
Purchase #5	$167.29	4.300%	$174.4835	$174.48	$174.50	$174.50
Purchase #6	$41.25	11.213%	$45.8754	$45.88	$45.90	$45.90
Purchase #7	$189.68	10.176%	$208.9818	$208.98	$209.00	$209.00
7 purchase totals =	$999.89		$1,079.9078	$1,079.91	$1,079.90	$1,080.00