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	$99.86	3.317%	$103.1724	$103.17	$103.15	$103.20
Purchase #2	$144.28	12.455%	$162.2501	$162.25	$162.25	$162.30
Purchase #3	$62.59	10.688%	$69.2796	$69.28	$69.30	$69.30
Purchase #4	$154.62	4.872%	$162.1531	$162.15	$162.15	$162.20
Purchase #5	$229.46	6.762%	$244.9761	$244.98	$245.00	$245.00
Purchase #6	$43.59	5.140%	$45.8305	$45.83	$45.85	$45.80
Purchase #7	$25.94	3.424%	$26.8282	$26.83	$26.85	$26.80
7 purchase totals =	$760.34		$814.4900	$814.49	$814.55	$814.60