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	$155.33	10.608%	$171.8074	$171.81	$171.80	$171.80
Purchase #2	$165.47	12.337%	$185.884	$185.88	$185.90	$185.90
Purchase #3	$59.81	8.847%	$65.1014	$65.10	$65.10	$65.10
Purchase #4	$167.42	5.278%	$176.2564	$176.26	$176.25	$176.30
Purchase #5	$30.76	7.620%	$33.1039	$33.10	$33.10	$33.10
Purchase #6	$119.51	4.543%	$124.9393	$124.94	$124.95	$124.90
Purchase #7	$129.93	11.441%	$144.7953	$144.80	$144.80	$144.80
7 purchase totals =	$828.23		$901.8877	$901.89	$901.90	$901.90