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	$208.48	11.760%	$232.9972	$233.00	$233.00	$233.00
Purchase #2	$60.29	8.873%	$65.6395	$65.64	$65.65	$65.60
Purchase #3	$210.63	4.390%	$219.8767	$219.88	$219.90	$219.90
Purchase #4	$17.50	7.521%	$18.8162	$18.82	$18.80	$18.80
Purchase #5	$116.71	9.129%	$127.3645	$127.36	$127.35	$127.40
Purchase #6	$25.74	6.183%	$27.3315	$27.33	$27.35	$27.30
Purchase #7	$81.69	9.719%	$89.6295	$89.63	$89.65	$89.60
7 purchase totals =	$721.04		$781.6551	$781.66	$781.70	$781.60