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	$206.72	4.625%	$216.2808	$216.28	$216.30	$216.30
Purchase #2	$50.74	10.138%	$55.884	$55.88	$55.90	$55.90
Purchase #3	$229.56	4.806%	$240.5927	$240.59	$240.60	$240.60
Purchase #4	$31.43	12.421%	$35.3339	$35.33	$35.35	$35.30
Purchase #5	$216.86	9.746%	$237.9952	$238.00	$238.00	$238.00
Purchase #6	$67.49	4.206%	$70.3286	$70.33	$70.35	$70.30
Purchase #7	$171.94	8.676%	$186.8575	$186.86	$186.85	$186.90
7 purchase totals =	$974.74		$1,043.2727	$1,043.27	$1,043.35	$1,043.30