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	$209.31	10.294%	$230.8564	$230.86	$230.85	$230.90
Purchase #2	$25.96	9.753%	$28.4919	$28.49	$28.50	$28.50
Purchase #3	$55.58	4.819%	$58.2584	$58.26	$58.25	$58.30
Purchase #4	$119.65	6.571%	$127.5122	$127.51	$127.50	$127.50
Purchase #5	$75.25	13.159%	$85.1521	$85.15	$85.15	$85.20
Purchase #6	$188.65	5.529%	$199.0805	$199.08	$199.10	$199.10
Purchase #7	$55.97	5.512%	$59.0551	$59.06	$59.05	$59.10
7 purchase totals =	$730.37		$788.4066	$788.41	$788.40	$788.60