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	$97.95	7.408%	$105.2061	$105.21	$105.20	$105.20
Purchase #2	$151.63	11.493%	$169.0568	$169.06	$169.05	$169.10
Purchase #3	$65.59	3.498%	$67.8843	$67.88	$67.90	$67.90
Purchase #4	$63.71	5.755%	$67.3765	$67.38	$67.40	$67.40
Purchase #5	$169.57	11.598%	$189.2367	$189.24	$189.25	$189.20
Purchase #6	$54.75	10.735%	$60.6274	$60.63	$60.65	$60.60
Purchase #7	$215.31	11.796%	$240.708	$240.71	$240.70	$240.70
7 purchase totals =	$818.51		$900.0958	$900.11	$900.15	$900.10