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	$198.70	7.357%	$213.3184	$213.32	$213.30	$213.30
Purchase #2	$94.39	9.358%	$103.223	$103.22	$103.20	$103.20
Purchase #3	$168.79	5.550%	$178.1578	$178.16	$178.15	$178.20
Purchase #4	$110.82	5.816%	$117.2653	$117.27	$117.25	$117.30
Purchase #5	$125.93	5.750%	$133.171	$133.17	$133.15	$133.20
Purchase #6	$82.42	3.293%	$85.1341	$85.13	$85.15	$85.10
Purchase #7	$165.89	13.803%	$188.7878	$188.79	$188.80	$188.80
7 purchase totals =	$946.94		$1,019.0574	$1,019.06	$1,019.00	$1,019.10