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	$127.64	4.364%	$133.2102	$133.21	$133.20	$133.20
Purchase #2	$96.47	13.191%	$109.1954	$109.20	$109.20	$109.20
Purchase #3	$22.60	12.446%	$25.4128	$25.41	$25.40	$25.40
Purchase #4	$101.26	13.131%	$114.5565	$114.56	$114.55	$114.60
Purchase #5	$77.86	6.409%	$82.85	$82.85	$82.85	$82.90
Purchase #6	$144.40	6.801%	$154.2206	$154.22	$154.20	$154.20
Purchase #7	$228.53	9.588%	$250.4415	$250.44	$250.45	$250.40
7 purchase totals =	$798.76		$869.8870	$869.89	$869.85	$869.90