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	$180.32	7.380%	$193.6276	$193.63	$193.65	$193.60
Purchase #2	$118.87	8.453%	$128.9181	$128.92	$128.90	$128.90
Purchase #3	$191.47	10.360%	$211.3063	$211.31	$211.30	$211.30
Purchase #4	$78.93	7.748%	$85.0455	$85.05	$85.05	$85.00
Purchase #5	$174.60	8.147%	$188.8247	$188.82	$188.80	$188.80
Purchase #6	$189.85	3.301%	$196.1169	$196.12	$196.10	$196.10
Purchase #7	$14.77	4.732%	$15.4689	$15.47	$15.45	$15.50
7 purchase totals =	$948.81		$1,019.3080	$1,019.32	$1,019.25	$1,019.20