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	$48.49	11.545%	$54.0882	$54.09	$54.10	$54.10
Purchase #2	$85.51	4.304%	$89.1904	$89.19	$89.20	$89.20
Purchase #3	$159.75	12.196%	$179.2331	$179.23	$179.25	$179.20
Purchase #4	$62.40	6.421%	$66.4067	$66.41	$66.40	$66.40
Purchase #5	$78.44	8.445%	$85.0643	$85.06	$85.05	$85.10
Purchase #6	$186.47	4.500%	$194.8612	$194.86	$194.85	$194.90
Purchase #7	$72.91	13.492%	$82.747	$82.75	$82.75	$82.70
7 purchase totals =	$693.97		$751.5909	$751.59	$751.60	$751.60