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	$218.37	3.432%	$225.8645	$225.86	$225.85	$225.90
Purchase #2	$89.55	10.285%	$98.7602	$98.76	$98.75	$98.80
Purchase #3	$245.45	9.210%	$268.0559	$268.06	$268.05	$268.10
Purchase #4	$65.33	9.834%	$71.7546	$71.75	$71.75	$71.80
Purchase #5	$43.47	3.815%	$45.1284	$45.13	$45.15	$45.10
Purchase #6	$26.75	12.668%	$30.1387	$30.14	$30.15	$30.10
Purchase #7	$19.31	9.758%	$21.1943	$21.19	$21.20	$21.20
7 purchase totals =	$708.23		$760.8966	$760.89	$760.90	$761.00