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	$61.25	4.537%	$64.0289	$64.03	$64.05	$64.00
Purchase #2	$26.46	6.550%	$28.1931	$28.19	$28.20	$28.20
Purchase #3	$91.93	4.776%	$96.3206	$96.32	$96.30	$96.30
Purchase #4	$33.71	13.123%	$38.1338	$38.13	$38.15	$38.10
Purchase #5	$31.96	8.373%	$34.636	$34.64	$34.65	$34.60
Purchase #6	$235.93	11.443%	$262.9275	$262.93	$262.95	$262.90
Purchase #7	$112.28	13.383%	$127.3064	$127.31	$127.30	$127.30
7 purchase totals =	$593.52		$651.5463	$651.55	$651.60	$651.40