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	$179.37	5.207%	$188.7098	$188.71	$188.70	$188.70
Purchase #2	$36.48	12.573%	$41.0666	$41.07	$41.05	$41.10
Purchase #3	$56.86	4.590%	$59.4699	$59.47	$59.45	$59.50
Purchase #4	$136.72	4.508%	$142.8833	$142.88	$142.90	$142.90
Purchase #5	$141.27	12.533%	$158.9754	$158.98	$159.00	$159.00
Purchase #6	$225.73	9.787%	$247.8222	$247.82	$247.80	$247.80
Purchase #7	$196.77	10.771%	$217.9641	$217.96	$217.95	$218.00
7 purchase totals =	$973.20		$1,056.8913	$1,056.89	$1,056.85	$1,057.00