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	$142.85	3.523%	$147.8826	$147.88	$147.90	$147.90
Purchase #2	$160.80	4.690%	$168.3415	$168.34	$168.35	$168.30
Purchase #3	$56.28	6.407%	$59.8859	$59.89	$59.90	$59.90
Purchase #4	$189.53	10.368%	$209.1805	$209.18	$209.20	$209.20
Purchase #5	$227.97	13.648%	$259.0833	$259.08	$259.10	$259.10
Purchase #6	$73.34	13.543%	$83.2724	$83.27	$83.25	$83.30
Purchase #7	$86.77	10.134%	$95.5633	$95.56	$95.55	$95.60
7 purchase totals =	$937.54		$1,023.2095	$1,023.20	$1,023.25	$1,023.30