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	$175.52	3.616%	$181.8668	$181.87	$181.85	$181.90
Purchase #2	$177.52	9.327%	$194.0773	$194.08	$194.10	$194.10
Purchase #3	$61.64	11.645%	$68.818	$68.82	$68.80	$68.80
Purchase #4	$93.31	3.393%	$96.476	$96.48	$96.50	$96.50
Purchase #5	$106.42	9.156%	$116.1638	$116.16	$116.15	$116.20
Purchase #6	$67.32	3.269%	$69.5207	$69.52	$69.50	$69.50
Purchase #7	$82.68	7.645%	$89.0009	$89.00	$89.00	$89.00
7 purchase totals =	$764.41		$815.9235	$815.93	$815.90	$816.00