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	$205.60	3.291%	$212.3663	$212.37	$212.35	$212.40
Purchase #2	$104.75	6.795%	$111.8678	$111.87	$111.85	$111.90
Purchase #3	$165.49	3.246%	$170.8618	$170.86	$170.85	$170.90
Purchase #4	$67.63	7.853%	$72.941	$72.94	$72.95	$72.90
Purchase #5	$84.96	13.122%	$96.1085	$96.11	$96.10	$96.10
Purchase #6	$223.32	9.736%	$245.0624	$245.06	$245.05	$245.10
Purchase #7	$191.30	4.832%	$200.5436	$200.54	$200.55	$200.50
7 purchase totals =	$1,043.05		$1,109.7514	$1,109.75	$1,109.70	$1,109.80