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	$181.42	4.207%	$189.0523	$189.05	$189.05	$189.10
Purchase #2	$242.51	12.601%	$273.0687	$273.07	$273.05	$273.10
Purchase #3	$69.29	7.335%	$74.3724	$74.37	$74.35	$74.40
Purchase #4	$36.31	3.552%	$37.5997	$37.60	$37.60	$37.60
Purchase #5	$144.46	12.178%	$162.0523	$162.05	$162.05	$162.10
Purchase #6	$79.46	7.524%	$85.4386	$85.44	$85.45	$85.40
Purchase #7	$234.60	9.497%	$256.88	$256.88	$256.90	$256.90
7 purchase totals =	$988.05		$1,078.4640	$1,078.46	$1,078.45	$1,078.60