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	$238.80	4.751%	$250.1454	$250.15	$250.15	$250.10
Purchase #2	$172.30	4.349%	$179.7933	$179.79	$179.80	$179.80
Purchase #3	$67.27	7.739%	$72.476	$72.48	$72.50	$72.50
Purchase #4	$77.39	11.282%	$86.1211	$86.12	$86.10	$86.10
Purchase #5	$235.44	12.200%	$264.1637	$264.16	$264.15	$264.20
Purchase #6	$32.38	11.699%	$36.1681	$36.17	$36.15	$36.20
Purchase #7	$156.32	11.314%	$174.006	$174.01	$174.00	$174.00
7 purchase totals =	$979.90		$1,062.8736	$1,062.88	$1,062.85	$1,062.90