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	$158.38	7.434%	$170.154	$170.15	$170.15	$170.20
Purchase #2	$141.49	7.298%	$151.8159	$151.82	$151.80	$151.80
Purchase #3	$75.47	3.446%	$78.0707	$78.07	$78.05	$78.10
Purchase #4	$66.92	9.415%	$73.2205	$73.22	$73.20	$73.20
Purchase #5	$153.27	7.347%	$164.5307	$164.53	$164.55	$164.50
Purchase #6	$191.61	3.620%	$198.5463	$198.55	$198.55	$198.50
Purchase #7	$167.44	11.727%	$187.0757	$187.08	$187.10	$187.10
7 purchase totals =	$954.58		$1,023.4138	$1,023.42	$1,023.40	$1,023.40