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	$155.88	7.548%	$167.6458	$167.65	$167.65	$167.60
Purchase #2	$147.58	12.665%	$166.271	$166.27	$166.25	$166.30
Purchase #3	$247.86	4.732%	$259.5887	$259.59	$259.60	$259.60
Purchase #4	$82.31	10.824%	$91.2192	$91.22	$91.20	$91.20
Purchase #5	$132.91	5.260%	$139.9011	$139.90	$139.90	$139.90
Purchase #6	$115.37	12.811%	$130.1501	$130.15	$130.15	$130.20
Purchase #7	$90.99	9.529%	$99.6604	$99.66	$99.65	$99.70
7 purchase totals =	$972.90		$1,054.4363	$1,054.44	$1,054.40	$1,054.50