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	$142.92	6.356%	$152.004	$152.00	$152.00	$152.00
Purchase #2	$152.54	9.787%	$167.4691	$167.47	$167.45	$167.50
Purchase #3	$173.93	13.817%	$197.9619	$197.96	$197.95	$198.00
Purchase #4	$50.35	10.236%	$55.5038	$55.50	$55.50	$55.50
Purchase #5	$204.39	12.785%	$230.5213	$230.52	$230.50	$230.50
Purchase #6	$87.25	10.407%	$96.3301	$96.33	$96.35	$96.30
Purchase #7	$127.96	11.580%	$142.7778	$142.78	$142.80	$142.80
7 purchase totals =	$939.34		$1,042.5680	$1,042.56	$1,042.55	$1,042.60