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	$69.34	5.157%	$72.9159	$72.92	$72.90	$72.90
Purchase #2	$72.97	7.844%	$78.6938	$78.69	$78.70	$78.70
Purchase #3	$26.88	11.619%	$30.0032	$30.00	$30.00	$30.00
Purchase #4	$178.30	7.329%	$191.3676	$191.37	$191.35	$191.40
Purchase #5	$73.93	6.804%	$78.9602	$78.96	$78.95	$79.00
Purchase #6	$92.28	3.498%	$95.508	$95.51	$95.50	$95.50
Purchase #7	$142.53	6.638%	$151.9911	$151.99	$152.00	$152.00
7 purchase totals =	$656.23		$699.4398	$699.44	$699.40	$699.50