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	$198.69	6.577%	$211.7578	$211.76	$211.75	$211.80
Purchase #2	$189.71	9.792%	$208.2864	$208.29	$208.30	$208.30
Purchase #3	$141.79	4.744%	$148.5165	$148.52	$148.50	$148.50
Purchase #4	$53.50	3.385%	$55.311	$55.31	$55.30	$55.30
Purchase #5	$95.49	10.442%	$105.4611	$105.46	$105.45	$105.50
Purchase #6	$85.31	7.803%	$91.9667	$91.97	$91.95	$92.00
Purchase #7	$250.44	9.311%	$273.7585	$273.76	$273.75	$273.80
7 purchase totals =	$1,014.93		$1,095.0580	$1,095.07	$1,095.00	$1,095.20