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	$167.67	11.292%	$186.6033	$186.60	$186.60	$186.60
Purchase #2	$78.39	11.281%	$87.2332	$87.23	$87.25	$87.20
Purchase #3	$49.38	5.396%	$52.0445	$52.04	$52.05	$52.00
Purchase #4	$143.66	13.298%	$162.7639	$162.76	$162.75	$162.80
Purchase #5	$180.97	10.808%	$200.5292	$200.53	$200.55	$200.50
Purchase #6	$164.91	3.842%	$171.2458	$171.25	$171.25	$171.20
Purchase #7	$35.75	12.786%	$40.321	$40.32	$40.30	$40.30
7 purchase totals =	$820.73		$900.7409	$900.73	$900.75	$900.60