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	$203.66	10.512%	$225.0687	$225.07	$225.05	$225.10
Purchase #2	$78.85	4.182%	$82.1475	$82.15	$82.15	$82.10
Purchase #3	$209.40	5.478%	$220.8709	$220.87	$220.85	$220.90
Purchase #4	$140.34	7.139%	$150.3589	$150.36	$150.35	$150.40
Purchase #5	$225.91	4.409%	$235.8704	$235.87	$235.85	$235.90
Purchase #6	$112.90	13.652%	$128.3131	$128.31	$128.30	$128.30
Purchase #7	$7.66	5.106%	$8.0511	$8.05	$8.05	$8.10
7 purchase totals =	$978.72		$1,050.6806	$1,050.68	$1,050.60	$1,050.80