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	$177.66	11.696%	$198.4391	$198.44	$198.45	$198.40
Purchase #2	$203.50	3.585%	$210.7955	$210.80	$210.80	$210.80
Purchase #3	$42.38	11.141%	$47.1016	$47.10	$47.10	$47.10
Purchase #4	$231.55	7.768%	$249.5368	$249.54	$249.55	$249.50
Purchase #5	$203.39	12.673%	$229.1656	$229.17	$229.15	$229.20
Purchase #6	$25.77	10.529%	$28.4833	$28.48	$28.50	$28.50
Purchase #7	$116.70	9.312%	$127.5671	$127.57	$127.55	$127.60
7 purchase totals =	$1,000.95		$1,091.0890	$1,091.10	$1,091.10	$1,091.10