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	$203.74	4.123%	$212.1402	$212.14	$212.15	$212.10
Purchase #2	$152.34	9.126%	$166.2425	$166.24	$166.25	$166.20
Purchase #3	$98.77	12.646%	$111.2605	$111.26	$111.25	$111.30
Purchase #4	$237.99	5.837%	$251.8815	$251.88	$251.90	$251.90
Purchase #5	$130.51	3.364%	$134.9004	$134.90	$134.90	$134.90
Purchase #6	$109.58	13.496%	$124.3689	$124.37	$124.35	$124.40
Purchase #7	$78.92	4.469%	$82.4469	$82.45	$82.45	$82.40
7 purchase totals =	$1,011.85		$1,083.2409	$1,083.24	$1,083.25	$1,083.20