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	$171.65	4.823%	$179.9287	$179.93	$179.95	$179.90
Purchase #2	$81.38	5.801%	$86.1009	$86.10	$86.10	$86.10
Purchase #3	$94.72	11.578%	$105.6867	$105.69	$105.70	$105.70
Purchase #4	$229.30	10.682%	$253.7938	$253.79	$253.80	$253.80
Purchase #5	$103.82	9.490%	$113.6725	$113.67	$113.65	$113.70
Purchase #6	$45.33	11.747%	$50.6549	$50.65	$50.65	$50.70
Purchase #7	$233.90	10.839%	$259.2524	$259.25	$259.25	$259.30
7 purchase totals =	$960.10		$1,049.0899	$1,049.08	$1,049.10	$1,049.20