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	$99.73	9.343%	$109.0478	$109.05	$109.05	$109.00
Purchase #2	$57.77	3.391%	$59.729	$59.73	$59.75	$59.70
Purchase #3	$58.70	8.171%	$63.4964	$63.50	$63.50	$63.50
Purchase #4	$245.73	11.228%	$273.3206	$273.32	$273.30	$273.30
Purchase #5	$163.64	11.107%	$181.8155	$181.82	$181.80	$181.80
Purchase #6	$210.79	10.707%	$233.3593	$233.36	$233.35	$233.40
Purchase #7	$99.67	5.277%	$104.9296	$104.93	$104.95	$104.90
7 purchase totals =	$936.03		$1,025.6982	$1,025.71	$1,025.70	$1,025.60