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	$174.49	12.781%	$196.7916	$196.79	$196.80	$196.80
Purchase #2	$151.39	10.288%	$166.965	$166.97	$166.95	$167.00
Purchase #3	$145.30	6.320%	$154.483	$154.48	$154.50	$154.50
Purchase #4	$79.37	11.679%	$88.6396	$88.64	$88.65	$88.60
Purchase #5	$48.85	12.436%	$54.925	$54.93	$54.95	$54.90
Purchase #6	$20.43	4.339%	$21.3165	$21.32	$21.30	$21.30
Purchase #7	$97.27	4.254%	$101.4079	$101.41	$101.40	$101.40
7 purchase totals =	$717.10		$784.5286	$784.54	$784.55	$784.50