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	$101.40	10.431%	$111.977	$111.98	$112.00	$112.00
Purchase #2	$196.62	10.402%	$217.0724	$217.07	$217.05	$217.10
Purchase #3	$196.78	12.722%	$221.8144	$221.81	$221.80	$221.80
Purchase #4	$30.61	7.133%	$32.7934	$32.79	$32.80	$32.80
Purchase #5	$24.41	11.845%	$27.3014	$27.30	$27.30	$27.30
Purchase #6	$195.82	13.498%	$222.2518	$222.25	$222.25	$222.30
Purchase #7	$241.40	10.649%	$267.1067	$267.11	$267.10	$267.10
7 purchase totals =	$987.04		$1,100.3171	$1,100.31	$1,100.30	$1,100.40