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	$175.85	7.108%	$188.3494	$188.35	$188.35	$188.30
Purchase #2	$235.83	13.666%	$268.0585	$268.06	$268.05	$268.10
Purchase #3	$27.92	5.849%	$29.553	$29.55	$29.55	$29.60
Purchase #4	$200.90	5.818%	$212.5884	$212.59	$212.60	$212.60
Purchase #5	$55.27	8.368%	$59.895	$59.90	$59.90	$59.90
Purchase #6	$171.82	9.547%	$188.2237	$188.22	$188.20	$188.20
Purchase #7	$13.90	5.379%	$14.6477	$14.65	$14.65	$14.60
7 purchase totals =	$881.49		$961.3157	$961.32	$961.30	$961.30