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	$160.42	8.859%	$174.6316	$174.63	$174.65	$174.60
Purchase #2	$199.27	6.356%	$211.9356	$211.94	$211.95	$211.90
Purchase #3	$82.28	6.457%	$87.5928	$87.59	$87.60	$87.60
Purchase #4	$83.75	10.355%	$92.4223	$92.42	$92.40	$92.40
Purchase #5	$234.87	9.404%	$256.9572	$256.96	$256.95	$257.00
Purchase #6	$201.72	6.716%	$215.2675	$215.27	$215.25	$215.30
Purchase #7	$104.58	9.111%	$114.1083	$114.11	$114.10	$114.10
7 purchase totals =	$1,066.89		$1,152.9153	$1,152.92	$1,152.90	$1,152.90