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	$193.47	3.539%	$200.3169	$200.32	$200.30	$200.30
Purchase #2	$108.31	7.740%	$116.6932	$116.69	$116.70	$116.70
Purchase #3	$47.50	8.389%	$51.4848	$51.48	$51.50	$51.50
Purchase #4	$56.97	4.134%	$59.3251	$59.33	$59.35	$59.30
Purchase #5	$5.41	8.817%	$5.887	$5.89	$5.90	$5.90
Purchase #6	$99.30	10.437%	$109.6639	$109.66	$109.65	$109.70
Purchase #7	$47.43	13.467%	$53.8174	$53.82	$53.80	$53.80
7 purchase totals =	$558.39		$597.1883	$597.19	$597.20	$597.20