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	$137.98	10.593%	$152.5962	$152.60	$152.60	$152.60
Purchase #2	$61.60	13.469%	$69.8969	$69.90	$69.90	$69.90
Purchase #3	$162.74	13.664%	$184.9768	$184.98	$185.00	$185.00
Purchase #4	$174.28	11.589%	$194.4773	$194.48	$194.50	$194.50
Purchase #5	$41.27	10.510%	$45.6075	$45.61	$45.60	$45.60
Purchase #6	$58.30	11.860%	$65.2144	$65.21	$65.20	$65.20
Purchase #7	$67.80	3.638%	$70.2666	$70.27	$70.25	$70.30
7 purchase totals =	$703.97		$783.0357	$783.05	$783.05	$783.10