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	$176.31	13.294%	$199.7487	$199.75	$199.75	$199.70
Purchase #2	$98.33	7.597%	$105.8001	$105.80	$105.80	$105.80
Purchase #3	$73.98	11.606%	$82.5661	$82.57	$82.55	$82.60
Purchase #4	$221.90	12.717%	$250.119	$250.12	$250.10	$250.10
Purchase #5	$25.74	9.458%	$28.1745	$28.17	$28.15	$28.20
Purchase #6	$96.80	3.241%	$99.9373	$99.94	$99.95	$99.90
Purchase #7	$250.87	11.309%	$279.2409	$279.24	$279.25	$279.20
7 purchase totals =	$943.93		$1,045.5866	$1,045.59	$1,045.55	$1,045.50