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	$144.52	3.411%	$149.4496	$149.45	$149.45	$149.40
Purchase #2	$83.85	3.682%	$86.9374	$86.94	$86.95	$86.90
Purchase #3	$146.79	13.823%	$167.0808	$167.08	$167.10	$167.10
Purchase #4	$170.91	12.275%	$191.8892	$191.89	$191.90	$191.90
Purchase #5	$239.94	11.755%	$268.1449	$268.14	$268.15	$268.10
Purchase #6	$123.34	3.383%	$127.5126	$127.51	$127.50	$127.50
Purchase #7	$180.56	3.338%	$186.5871	$186.59	$186.60	$186.60
7 purchase totals =	$1,089.91		$1,177.6016	$1,177.60	$1,177.65	$1,177.50