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	$214.36	6.728%	$228.7821	$228.78	$228.80	$228.80
Purchase #2	$205.76	3.402%	$212.76	$212.76	$212.75	$212.80
Purchase #3	$201.40	5.175%	$211.8225	$211.82	$211.80	$211.80
Purchase #4	$58.90	11.237%	$65.5186	$65.52	$65.50	$65.50
Purchase #5	$79.60	5.293%	$83.8132	$83.81	$83.80	$83.80
Purchase #6	$174.88	7.531%	$188.0502	$188.05	$188.05	$188.10
Purchase #7	$109.30	13.348%	$123.8894	$123.89	$123.90	$123.90
7 purchase totals =	$1,044.20		$1,114.6360	$1,114.63	$1,114.60	$1,114.70