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	$114.76	11.337%	$127.7703	$127.77	$127.75	$127.80
Purchase #2	$173.72	7.602%	$186.9262	$186.93	$186.95	$186.90
Purchase #3	$123.92	7.708%	$133.4718	$133.47	$133.45	$133.50
Purchase #4	$215.50	6.458%	$229.417	$229.42	$229.40	$229.40
Purchase #5	$148.31	6.132%	$157.4044	$157.40	$157.40	$157.40
Purchase #6	$127.74	9.455%	$139.8178	$139.82	$139.80	$139.80
Purchase #7	$185.37	12.815%	$209.1252	$209.13	$209.15	$209.10
7 purchase totals =	$1,089.32		$1,183.9327	$1,183.94	$1,183.90	$1,183.90