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	$99.76	10.740%	$110.4742	$110.47	$110.45	$110.50
Purchase #2	$171.27	11.598%	$191.1339	$191.13	$191.15	$191.10
Purchase #3	$116.55	6.271%	$123.8589	$123.86	$123.85	$123.90
Purchase #4	$226.84	3.727%	$235.2943	$235.29	$235.30	$235.30
Purchase #5	$198.64	6.545%	$211.641	$211.64	$211.65	$211.60
Purchase #6	$119.93	6.512%	$127.7398	$127.74	$127.75	$127.70
Purchase #7	$227.90	6.224%	$242.0845	$242.08	$242.10	$242.10
7 purchase totals =	$1,160.89		$1,242.2266	$1,242.21	$1,242.25	$1,242.20