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	$138.26	6.757%	$147.6022	$147.60	$147.60	$147.60
Purchase #2	$122.52	13.845%	$139.4829	$139.48	$139.50	$139.50
Purchase #3	$75.73	5.659%	$80.0156	$80.02	$80.00	$80.00
Purchase #4	$207.27	12.463%	$233.1021	$233.10	$233.10	$233.10
Purchase #5	$153.98	11.805%	$172.1573	$172.16	$172.15	$172.20
Purchase #6	$87.44	13.286%	$99.0573	$99.06	$99.05	$99.10
Purchase #7	$196.29	9.172%	$214.2937	$214.29	$214.30	$214.30
7 purchase totals =	$981.49		$1,085.7111	$1,085.71	$1,085.70	$1,085.80