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	$121.63	7.700%	$130.9955	$131.00	$131.00	$131.00
Purchase #2	$224.42	9.216%	$245.1025	$245.10	$245.10	$245.10
Purchase #3	$157.42	4.727%	$164.8612	$164.86	$164.85	$164.90
Purchase #4	$56.87	10.779%	$63	$63.00	$63.00	$63.00
Purchase #5	$83.77	8.370%	$90.7815	$90.78	$90.80	$90.80
Purchase #6	$116.77	11.331%	$130.0012	$130.00	$130.00	$130.00
Purchase #7	$177.35	4.539%	$185.3999	$185.40	$185.40	$185.40
7 purchase totals =	$938.23		$1,010.1418	$1,010.14	$1,010.15	$1,010.20