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	$167.83	8.627%	$182.3087	$182.31	$182.30	$182.30
Purchase #2	$209.69	12.666%	$236.2493	$236.25	$236.25	$236.20
Purchase #3	$135.90	8.262%	$147.1281	$147.13	$147.15	$147.10
Purchase #4	$27.50	13.424%	$31.1916	$31.19	$31.20	$31.20
Purchase #5	$79.96	11.604%	$89.2386	$89.24	$89.25	$89.20
Purchase #6	$85.98	5.422%	$90.6418	$90.64	$90.65	$90.60
Purchase #7	$89.41	10.819%	$99.0833	$99.08	$99.10	$99.10
7 purchase totals =	$796.27		$875.8414	$875.84	$875.90	$875.70