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	$184.56	6.294%	$196.1762	$196.18	$196.20	$196.20
Purchase #2	$177.98	5.372%	$187.5411	$187.54	$187.55	$187.50
Purchase #3	$101.98	7.648%	$109.7794	$109.78	$109.80	$109.80
Purchase #4	$78.47	13.734%	$89.2471	$89.25	$89.25	$89.20
Purchase #5	$25.76	4.510%	$26.9218	$26.92	$26.90	$26.90
Purchase #6	$55.95	13.395%	$63.4445	$63.44	$63.45	$63.40
Purchase #7	$64.73	8.397%	$70.1654	$70.17	$70.15	$70.20
7 purchase totals =	$689.43		$743.2755	$743.28	$743.30	$743.20