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	$191.78	4.309%	$200.0438	$200.04	$200.05	$200.00
Purchase #2	$105.55	3.728%	$109.4849	$109.48	$109.50	$109.50
Purchase #3	$147.29	7.497%	$158.3323	$158.33	$158.35	$158.30
Purchase #4	$161.30	11.488%	$179.8301	$179.83	$179.85	$179.80
Purchase #5	$234.49	11.764%	$262.0754	$262.08	$262.10	$262.10
Purchase #6	$30.47	4.738%	$31.9137	$31.91	$31.90	$31.90
Purchase #7	$52.33	11.490%	$58.3427	$58.34	$58.35	$58.30
7 purchase totals =	$923.21		$1,000.0229	$1,000.01	$1,000.10	$999.90