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	$68.47	4.310%	$71.4211	$71.42	$71.40	$71.40
Purchase #2	$190.63	4.200%	$198.6365	$198.64	$198.65	$198.60
Purchase #3	$101.64	9.185%	$110.9756	$110.98	$111.00	$111.00
Purchase #4	$117.88	11.409%	$131.3289	$131.33	$131.35	$131.30
Purchase #5	$160.34	5.284%	$168.8124	$168.81	$168.80	$168.80
Purchase #6	$41.57	8.405%	$45.064	$45.06	$45.05	$45.10
Purchase #7	$54.27	10.734%	$60.0953	$60.10	$60.10	$60.10
7 purchase totals =	$734.80		$786.3338	$786.34	$786.35	$786.30