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	$188.34	4.117%	$196.094	$196.09	$196.10	$196.10
Purchase #2	$228.69	3.268%	$236.1636	$236.16	$236.15	$236.20
Purchase #3	$147.43	12.272%	$165.5226	$165.52	$165.50	$165.50
Purchase #4	$22.92	4.517%	$23.9553	$23.96	$23.95	$24.00
Purchase #5	$238.30	13.798%	$271.1806	$271.18	$271.20	$271.20
Purchase #6	$47.27	12.298%	$53.0833	$53.08	$53.10	$53.10
Purchase #7	$74.91	9.533%	$82.0512	$82.05	$82.05	$82.10
7 purchase totals =	$947.86		$1,028.0506	$1,028.04	$1,028.05	$1,028.20