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	$130.39	10.483%	$144.0588	$144.06	$144.05	$144.10
Purchase #2	$91.47	7.165%	$98.0238	$98.02	$98.00	$98.00
Purchase #3	$192.76	9.383%	$210.8467	$210.85	$210.85	$210.80
Purchase #4	$141.65	4.117%	$147.4817	$147.48	$147.50	$147.50
Purchase #5	$89.74	13.204%	$101.5893	$101.59	$101.60	$101.60
Purchase #6	$179.95	3.862%	$186.8997	$186.90	$186.90	$186.90
Purchase #7	$183.56	4.754%	$192.2864	$192.29	$192.30	$192.30
7 purchase totals =	$1,009.52		$1,081.1864	$1,081.19	$1,081.20	$1,081.20