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	$174.36	12.439%	$196.0486	$196.05	$196.05	$196.00
Purchase #2	$92.78	9.727%	$101.8047	$101.80	$101.80	$101.80
Purchase #3	$56.28	11.139%	$62.549	$62.55	$62.55	$62.50
Purchase #4	$50.31	13.404%	$57.0536	$57.05	$57.05	$57.10
Purchase #5	$83.55	9.833%	$91.7655	$91.77	$91.75	$91.80
Purchase #6	$221.25	11.333%	$246.3243	$246.32	$246.30	$246.30
Purchase #7	$177.42	9.848%	$194.8923	$194.89	$194.90	$194.90
7 purchase totals =	$855.95		$950.4380	$950.43	$950.40	$950.40