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	$171.28	4.693%	$179.3182	$179.32	$179.30	$179.30
Purchase #2	$96.83	13.310%	$109.7181	$109.72	$109.70	$109.70
Purchase #3	$143.33	10.849%	$158.8799	$158.88	$158.90	$158.90
Purchase #4	$7.66	13.842%	$8.7203	$8.72	$8.70	$8.70
Purchase #5	$245.28	4.651%	$256.688	$256.69	$256.70	$256.70
Purchase #6	$158.27	10.654%	$175.1321	$175.13	$175.15	$175.10
Purchase #7	$130.56	9.438%	$142.8823	$142.88	$142.90	$142.90
7 purchase totals =	$953.21		$1,031.3389	$1,031.34	$1,031.35	$1,031.30