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	$220.74	12.141%	$247.54	$247.54	$247.55	$247.50
Purchase #2	$167.66	7.113%	$179.5857	$179.59	$179.60	$179.60
Purchase #3	$194.51	8.133%	$210.3295	$210.33	$210.35	$210.30
Purchase #4	$226.88	7.507%	$243.9119	$243.91	$243.90	$243.90
Purchase #5	$165.83	10.251%	$182.8292	$182.83	$182.85	$182.80
Purchase #6	$18.97	8.357%	$20.5553	$20.56	$20.55	$20.60
Purchase #7	$64.63	5.171%	$67.972	$67.97	$67.95	$68.00
7 purchase totals =	$1,059.22		$1,152.7236	$1,152.73	$1,152.75	$1,152.70