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	$17.84	11.347%	$19.8643	$19.86	$19.85	$19.90
Purchase #2	$65.98	11.294%	$73.4318	$73.43	$73.45	$73.40
Purchase #3	$17.88	12.668%	$20.145	$20.15	$20.15	$20.10
Purchase #4	$46.80	10.314%	$51.627	$51.63	$51.65	$51.60
Purchase #5	$105.82	8.261%	$114.5618	$114.56	$114.55	$114.60
Purchase #6	$114.91	11.153%	$127.7259	$127.73	$127.75	$127.70
Purchase #7	$49.99	7.845%	$53.9117	$53.91	$53.90	$53.90
7 purchase totals =	$419.22		$461.2675	$461.27	$461.30	$461.20