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	$123.42	5.767%	$130.5376	$130.54	$130.55	$130.50
Purchase #2	$242.84	6.681%	$259.0641	$259.06	$259.05	$259.10
Purchase #3	$234.91	12.565%	$264.4264	$264.43	$264.45	$264.40
Purchase #4	$66.46	10.444%	$73.4011	$73.40	$73.40	$73.40
Purchase #5	$111.70	12.322%	$125.4637	$125.46	$125.45	$125.50
Purchase #6	$36.36	3.478%	$37.6246	$37.62	$37.60	$37.60
Purchase #7	$102.96	13.533%	$116.8936	$116.89	$116.90	$116.90
7 purchase totals =	$918.65		$1,007.4111	$1,007.40	$1,007.40	$1,007.40