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	$132.50	13.288%	$150.1066	$150.11	$150.10	$150.10
Purchase #2	$240.95	3.671%	$249.7953	$249.80	$249.80	$249.80
Purchase #3	$165.46	3.845%	$171.8219	$171.82	$171.80	$171.80
Purchase #4	$202.73	9.428%	$221.8434	$221.84	$221.85	$221.80
Purchase #5	$58.89	12.560%	$66.2866	$66.29	$66.30	$66.30
Purchase #6	$95.89	10.510%	$105.968	$105.97	$105.95	$106.00
Purchase #7	$132.69	13.489%	$150.5886	$150.59	$150.60	$150.60
7 purchase totals =	$1,029.11		$1,116.4104	$1,116.42	$1,116.40	$1,116.40