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	$154.83	3.356%	$160.0261	$160.03	$160.05	$160.00
Purchase #2	$182.69	4.680%	$191.2399	$191.24	$191.25	$191.20
Purchase #3	$160.59	6.606%	$171.1986	$171.20	$171.20	$171.20
Purchase #4	$60.89	10.120%	$67.0521	$67.05	$67.05	$67.10
Purchase #5	$112.86	12.755%	$127.2553	$127.26	$127.25	$127.30
Purchase #6	$100.76	11.196%	$112.0411	$112.04	$112.05	$112.00
Purchase #7	$184.38	10.266%	$203.3085	$203.31	$203.30	$203.30
7 purchase totals =	$957.00		$1,032.1216	$1,032.13	$1,032.15	$1,032.10