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	$72.42	13.200%	$81.9794	$81.98	$82.00	$82.00
Purchase #2	$29.56	13.764%	$33.6286	$33.63	$33.65	$33.60
Purchase #3	$24.61	11.818%	$27.5184	$27.52	$27.50	$27.50
Purchase #4	$38.32	8.288%	$41.496	$41.50	$41.50	$41.50
Purchase #5	$153.28	7.485%	$164.753	$164.75	$164.75	$164.80
Purchase #6	$60.41	7.753%	$65.0936	$65.09	$65.10	$65.10
Purchase #7	$79.88	8.581%	$86.7345	$86.73	$86.75	$86.70
7 purchase totals =	$458.48		$501.2035	$501.20	$501.25	$501.20