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	$196.76	13.386%	$223.0983	$223.10	$223.10	$223.10
Purchase #2	$37.64	4.650%	$39.3903	$39.39	$39.40	$39.40
Purchase #3	$162.94	3.462%	$168.581	$168.58	$168.60	$168.60
Purchase #4	$32.31	10.287%	$35.6337	$35.63	$35.65	$35.60
Purchase #5	$181.64	13.359%	$205.9053	$205.91	$205.90	$205.90
Purchase #6	$198.34	4.759%	$207.779	$207.78	$207.80	$207.80
Purchase #7	$58.42	10.417%	$64.5056	$64.51	$64.50	$64.50
7 purchase totals =	$868.05		$944.8932	$944.90	$944.95	$944.90