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	$110.53	7.798%	$119.1491	$119.15	$119.15	$119.10
Purchase #2	$71.68	12.157%	$80.3941	$80.39	$80.40	$80.40
Purchase #3	$38.83	12.372%	$43.634	$43.63	$43.65	$43.60
Purchase #4	$67.53	5.602%	$71.313	$71.31	$71.30	$71.30
Purchase #5	$57.66	12.132%	$64.6553	$64.66	$64.65	$64.70
Purchase #6	$225.29	13.242%	$255.1229	$255.12	$255.10	$255.10
Purchase #7	$201.88	7.757%	$217.5398	$217.54	$217.55	$217.50
7 purchase totals =	$773.40		$851.8082	$851.80	$851.80	$851.70