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	$33.80	5.704%	$35.728	$35.73	$35.75	$35.70
Purchase #2	$147.52	10.391%	$162.8488	$162.85	$162.85	$162.80
Purchase #3	$48.53	5.122%	$51.0157	$51.02	$51.00	$51.00
Purchase #4	$229.73	3.840%	$238.5516	$238.55	$238.55	$238.60
Purchase #5	$233.60	9.109%	$254.8786	$254.88	$254.90	$254.90
Purchase #6	$11.58	8.249%	$12.5352	$12.54	$12.55	$12.50
Purchase #7	$220.36	13.591%	$250.3091	$250.31	$250.30	$250.30
7 purchase totals =	$925.12		$1,005.8670	$1,005.88	$1,005.90	$1,005.80