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	$203.62	12.514%	$229.101	$229.10	$229.10	$229.10
Purchase #2	$240.86	12.227%	$270.31	$270.31	$270.30	$270.30
Purchase #3	$6.26	9.666%	$6.8651	$6.87	$6.85	$6.90
Purchase #4	$67.72	3.375%	$70.0056	$70.01	$70.00	$70.00
Purchase #5	$249.57	6.547%	$265.9093	$265.91	$265.90	$265.90
Purchase #6	$178.53	4.123%	$185.8908	$185.89	$185.90	$185.90
Purchase #7	$63.89	6.348%	$67.9457	$67.95	$67.95	$67.90
7 purchase totals =	$1,010.45		$1,096.0275	$1,096.04	$1,096.00	$1,096.00