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	$215.99	3.665%	$223.906	$223.91	$223.90	$223.90
Purchase #2	$234.76	5.128%	$246.7985	$246.80	$246.80	$246.80
Purchase #3	$82.37	10.443%	$90.9719	$90.97	$90.95	$91.00
Purchase #4	$167.88	9.797%	$184.3272	$184.33	$184.35	$184.30
Purchase #5	$193.37	9.118%	$211.0015	$211.00	$211.00	$211.00
Purchase #6	$237.84	3.185%	$245.4152	$245.42	$245.40	$245.40
Purchase #7	$56.40	6.211%	$59.903	$59.90	$59.90	$59.90
7 purchase totals =	$1,188.61		$1,262.3233	$1,262.33	$1,262.30	$1,262.30