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	$217.80	5.133%	$228.9797	$228.98	$229.00	$229.00
Purchase #2	$235.27	9.221%	$256.9642	$256.96	$256.95	$257.00
Purchase #3	$186.54	5.266%	$196.3632	$196.36	$196.35	$196.40
Purchase #4	$115.94	12.559%	$130.5009	$130.50	$130.50	$130.50
Purchase #5	$72.86	5.640%	$76.9693	$76.97	$76.95	$77.00
Purchase #6	$109.67	4.222%	$114.3003	$114.30	$114.30	$114.30
Purchase #7	$65.43	3.685%	$67.8411	$67.84	$67.85	$67.80
7 purchase totals =	$1,003.51		$1,071.9187	$1,071.91	$1,071.90	$1,072.00