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	$63.40	6.359%	$67.4316	$67.43	$67.45	$67.40
Purchase #2	$132.49	12.275%	$148.7531	$148.75	$148.75	$148.80
Purchase #3	$207.40	6.807%	$221.5177	$221.52	$221.50	$221.50
Purchase #4	$91.33	8.614%	$99.1972	$99.20	$99.20	$99.20
Purchase #5	$38.88	12.274%	$43.6521	$43.65	$43.65	$43.70
Purchase #6	$46.88	12.504%	$52.7419	$52.74	$52.75	$52.70
Purchase #7	$93.54	8.465%	$101.4582	$101.46	$101.45	$101.50
7 purchase totals =	$673.92		$734.7518	$734.75	$734.75	$734.80