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	$31.78	11.487%	$35.4306	$35.43	$35.45	$35.40
Purchase #2	$224.27	4.339%	$234.0011	$234.00	$234.00	$234.00
Purchase #3	$147.55	6.304%	$156.8516	$156.85	$156.85	$156.90
Purchase #4	$54.51	7.480%	$58.5873	$58.59	$58.60	$58.60
Purchase #5	$232.44	6.843%	$248.3459	$248.35	$248.35	$248.30
Purchase #6	$229.75	5.539%	$242.4759	$242.48	$242.50	$242.50
Purchase #7	$82.89	7.511%	$89.1159	$89.12	$89.10	$89.10
7 purchase totals =	$1,003.19		$1,064.8083	$1,064.82	$1,064.85	$1,064.80