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	$146.74	6.400%	$156.1314	$156.13	$156.15	$156.10
Purchase #2	$110.32	13.113%	$124.7863	$124.79	$124.80	$124.80
Purchase #3	$101.57	4.417%	$106.0563	$106.06	$106.05	$106.10
Purchase #4	$37.29	8.135%	$40.3235	$40.32	$40.30	$40.30
Purchase #5	$84.80	13.189%	$95.9843	$95.98	$96.00	$96.00
Purchase #6	$205.32	4.516%	$214.5923	$214.59	$214.60	$214.60
Purchase #7	$245.85	13.151%	$278.1817	$278.18	$278.20	$278.20
7 purchase totals =	$931.89		$1,016.0558	$1,016.05	$1,016.10	$1,016.10