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	$161.36	10.701%	$178.6271	$178.63	$178.65	$178.60
Purchase #2	$142.31	10.130%	$156.726	$156.73	$156.75	$156.70
Purchase #3	$31.31	5.583%	$33.058	$33.06	$33.05	$33.10
Purchase #4	$114.89	12.131%	$128.8273	$128.83	$128.85	$128.80
Purchase #5	$130.84	12.707%	$147.4658	$147.47	$147.45	$147.50
Purchase #6	$156.72	13.785%	$178.3239	$178.32	$178.30	$178.30
Purchase #7	$238.55	10.216%	$262.9203	$262.92	$262.90	$262.90
7 purchase totals =	$975.98		$1,085.9484	$1,085.96	$1,085.95	$1,085.90