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	$150.60	3.463%	$155.8153	$155.82	$155.80	$155.80
Purchase #2	$181.41	8.508%	$196.8444	$196.84	$196.85	$196.80
Purchase #3	$222.92	7.777%	$240.2565	$240.26	$240.25	$240.30
Purchase #4	$191.44	4.645%	$200.3324	$200.33	$200.35	$200.30
Purchase #5	$175.30	5.574%	$185.0712	$185.07	$185.05	$185.10
Purchase #6	$160.83	3.813%	$166.9624	$166.96	$166.95	$167.00
Purchase #7	$120.40	11.414%	$134.1425	$134.14	$134.15	$134.10
7 purchase totals =	$1,202.90		$1,279.4247	$1,279.42	$1,279.40	$1,279.40