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	$173.77	5.850%	$183.9355	$183.94	$183.95	$183.90
Purchase #2	$94.79	7.482%	$101.8822	$101.88	$101.90	$101.90
Purchase #3	$205.41	10.265%	$226.4953	$226.50	$226.50	$226.50
Purchase #4	$229.59	8.292%	$248.6276	$248.63	$248.65	$248.60
Purchase #5	$155.38	4.847%	$162.9113	$162.91	$162.90	$162.90
Purchase #6	$43.75	7.279%	$46.9346	$46.93	$46.95	$46.90
Purchase #7	$84.79	5.673%	$89.6001	$89.60	$89.60	$89.60
7 purchase totals =	$987.48		$1,060.3866	$1,060.39	$1,060.45	$1,060.30