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	$75.92	10.469%	$83.8681	$83.87	$83.85	$83.90
Purchase #2	$40.40	13.773%	$45.9643	$45.96	$45.95	$46.00
Purchase #3	$182.75	5.677%	$193.1247	$193.12	$193.10	$193.10
Purchase #4	$245.62	7.135%	$263.145	$263.15	$263.15	$263.10
Purchase #5	$216.93	7.446%	$233.0826	$233.08	$233.10	$233.10
Purchase #6	$48.61	13.438%	$55.1422	$55.14	$55.15	$55.10
Purchase #7	$181.93	8.237%	$196.9156	$196.92	$196.90	$196.90
7 purchase totals =	$992.16		$1,071.2425	$1,071.24	$1,071.20	$1,071.20