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	$179.49	3.360%	$185.5209	$185.52	$185.50	$185.50
Purchase #2	$148.45	5.663%	$156.8567	$156.86	$156.85	$156.90
Purchase #3	$241.94	5.656%	$255.6241	$255.62	$255.60	$255.60
Purchase #4	$89.35	6.450%	$95.1131	$95.11	$95.10	$95.10
Purchase #5	$240.72	9.429%	$263.4175	$263.42	$263.40	$263.40
Purchase #6	$130.70	6.398%	$139.0622	$139.06	$139.05	$139.10
Purchase #7	$249.36	9.514%	$273.0841	$273.08	$273.10	$273.10
7 purchase totals =	$1,280.01		$1,368.6786	$1,368.67	$1,368.60	$1,368.70