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	$96.36	9.510%	$105.5238	$105.52	$105.50	$105.50
Purchase #2	$54.97	7.768%	$59.2401	$59.24	$59.25	$59.20
Purchase #3	$243.49	12.405%	$273.6949	$273.69	$273.70	$273.70
Purchase #4	$153.47	11.804%	$171.5856	$171.59	$171.60	$171.60
Purchase #5	$167.92	10.415%	$185.4089	$185.41	$185.40	$185.40
Purchase #6	$184.94	5.485%	$195.084	$195.08	$195.10	$195.10
Purchase #7	$5.94	13.633%	$6.7498	$6.75	$6.75	$6.70
7 purchase totals =	$907.09		$997.2871	$997.28	$997.30	$997.20