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	$185.75	10.139%	$204.5832	$204.58	$204.60	$204.60
Purchase #2	$105.63	4.568%	$110.4552	$110.46	$110.45	$110.50
Purchase #3	$86.69	3.307%	$89.5568	$89.56	$89.55	$89.60
Purchase #4	$212.78	10.726%	$235.6028	$235.60	$235.60	$235.60
Purchase #5	$116.86	10.319%	$128.9188	$128.92	$128.90	$128.90
Purchase #6	$167.73	4.652%	$175.5328	$175.53	$175.55	$175.50
Purchase #7	$103.64	5.785%	$109.6356	$109.64	$109.65	$109.60
7 purchase totals =	$979.08		$1,054.2852	$1,054.29	$1,054.30	$1,054.30