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	$30.69	5.672%	$32.4307	$32.43	$32.45	$32.40
Purchase #2	$104.53	9.452%	$114.4102	$114.41	$114.40	$114.40
Purchase #3	$36.32	11.824%	$40.6145	$40.61	$40.60	$40.60
Purchase #4	$239.88	8.140%	$259.4062	$259.41	$259.40	$259.40
Purchase #5	$45.38	13.755%	$51.622	$51.62	$51.60	$51.60
Purchase #6	$98.38	11.472%	$109.6662	$109.67	$109.65	$109.70
Purchase #7	$237.68	7.829%	$256.288	$256.29	$256.30	$256.30
7 purchase totals =	$792.86		$864.4378	$864.44	$864.40	$864.40