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	$60.79	10.390%	$67.1061	$67.11	$67.10	$67.10
Purchase #2	$96.94	7.531%	$104.2406	$104.24	$104.25	$104.20
Purchase #3	$6.29	4.310%	$6.5611	$6.56	$6.55	$6.60
Purchase #4	$80.25	3.279%	$82.8814	$82.88	$82.90	$82.90
Purchase #5	$211.76	8.314%	$229.3657	$229.37	$229.35	$229.40
Purchase #6	$108.86	9.355%	$119.0439	$119.04	$119.05	$119.00
Purchase #7	$110.31	3.247%	$113.8918	$113.89	$113.90	$113.90
7 purchase totals =	$675.20		$723.0906	$723.09	$723.10	$723.10