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	$177.28	9.719%	$194.5098	$194.51	$194.50	$194.50
Purchase #2	$179.35	5.158%	$188.6009	$188.60	$188.60	$188.60
Purchase #3	$51.46	13.348%	$58.3289	$58.33	$58.35	$58.30
Purchase #4	$166.89	4.337%	$174.128	$174.13	$174.15	$174.10
Purchase #5	$133.38	6.568%	$142.1404	$142.14	$142.15	$142.10
Purchase #6	$173.33	13.571%	$196.8526	$196.85	$196.85	$196.90
Purchase #7	$62.54	6.700%	$66.7302	$66.73	$66.75	$66.70
7 purchase totals =	$944.23		$1,021.2908	$1,021.29	$1,021.35	$1,021.20