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	$160.27	13.818%	$182.4161	$182.42	$182.40	$182.40
Purchase #2	$120.70	13.645%	$137.1695	$137.17	$137.15	$137.20
Purchase #3	$15.41	3.497%	$15.9489	$15.95	$15.95	$15.90
Purchase #4	$116.25	10.589%	$128.5597	$128.56	$128.55	$128.60
Purchase #5	$123.32	6.793%	$131.6971	$131.70	$131.70	$131.70
Purchase #6	$76.37	7.552%	$82.1375	$82.14	$82.15	$82.10
Purchase #7	$165.54	6.390%	$176.118	$176.12	$176.10	$176.10
7 purchase totals =	$777.86		$854.0468	$854.06	$854.00	$854.00