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	$162.49	10.500%	$179.5515	$179.55	$179.55	$179.60
Purchase #2	$205.69	5.191%	$216.3674	$216.37	$216.35	$216.40
Purchase #3	$149.94	3.504%	$155.1939	$155.19	$155.20	$155.20
Purchase #4	$99.66	6.474%	$106.112	$106.11	$106.10	$106.10
Purchase #5	$29.83	13.250%	$33.7825	$33.78	$33.80	$33.80
Purchase #6	$244.40	8.807%	$265.9243	$265.92	$265.90	$265.90
Purchase #7	$31.30	4.107%	$32.5855	$32.59	$32.60	$32.60
7 purchase totals =	$923.31		$989.5171	$989.51	$989.50	$989.60