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	$48.94	5.798%	$51.7775	$51.78	$51.80	$51.80
Purchase #2	$233.95	6.469%	$249.0842	$249.08	$249.10	$249.10
Purchase #3	$50.90	5.405%	$53.6511	$53.65	$53.65	$53.70
Purchase #4	$50.76	9.384%	$55.5233	$55.52	$55.50	$55.50
Purchase #5	$238.41	12.467%	$268.1326	$268.13	$268.15	$268.10
Purchase #6	$217.35	11.569%	$242.4952	$242.50	$242.50	$242.50
Purchase #7	$83.67	9.427%	$91.5576	$91.56	$91.55	$91.60
7 purchase totals =	$923.98		$1,012.2215	$1,012.22	$1,012.25	$1,012.30