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	$81.55	4.829%	$85.488	$85.49	$85.50	$85.50
Purchase #2	$79.76	13.221%	$90.3051	$90.31	$90.30	$90.30
Purchase #3	$94.46	5.791%	$99.9302	$99.93	$99.95	$99.90
Purchase #4	$59.49	7.160%	$63.7495	$63.75	$63.75	$63.70
Purchase #5	$204.32	9.682%	$224.1023	$224.10	$224.10	$224.10
Purchase #6	$179.54	11.458%	$200.1117	$200.11	$200.10	$200.10
Purchase #7	$219.64	12.414%	$246.9061	$246.91	$246.90	$246.90
7 purchase totals =	$918.76		$1,010.5929	$1,010.60	$1,010.60	$1,010.50