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	$47.50	11.782%	$53.0965	$53.10	$53.10	$53.10
Purchase #2	$92.89	3.472%	$96.1151	$96.12	$96.10	$96.10
Purchase #3	$119.45	3.586%	$123.7335	$123.73	$123.75	$123.70
Purchase #4	$41.54	13.771%	$47.2605	$47.26	$47.25	$47.30
Purchase #5	$168.64	4.304%	$175.8983	$175.90	$175.90	$175.90
Purchase #6	$177.86	5.227%	$187.1567	$187.16	$187.15	$187.20
Purchase #7	$241.51	12.234%	$271.0563	$271.06	$271.05	$271.10
7 purchase totals =	$889.39		$954.3169	$954.33	$954.30	$954.40