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	$123.41	10.269%	$136.083	$136.08	$136.10	$136.10
Purchase #2	$56.25	5.729%	$59.4726	$59.47	$59.45	$59.50
Purchase #3	$167.65	3.865%	$174.1297	$174.13	$174.15	$174.10
Purchase #4	$81.39	10.348%	$89.8122	$89.81	$89.80	$89.80
Purchase #5	$16.76	7.164%	$17.9607	$17.96	$17.95	$18.00
Purchase #6	$101.95	7.236%	$109.3271	$109.33	$109.35	$109.30
Purchase #7	$106.51	9.717%	$116.8596	$116.86	$116.85	$116.90
7 purchase totals =	$653.92		$703.6449	$703.64	$703.65	$703.70