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	$86.60	3.443%	$89.5816	$89.58	$89.60	$89.60
Purchase #2	$189.84	11.432%	$211.5425	$211.54	$211.55	$211.50
Purchase #3	$212.65	11.223%	$236.5157	$236.52	$236.50	$236.50
Purchase #4	$209.87	3.685%	$217.6037	$217.60	$217.60	$217.60
Purchase #5	$6.77	9.107%	$7.3865	$7.39	$7.40	$7.40
Purchase #6	$137.55	10.710%	$152.2816	$152.28	$152.30	$152.30
Purchase #7	$39.36	6.413%	$41.8842	$41.88	$41.90	$41.90
7 purchase totals =	$882.64		$956.7958	$956.79	$956.85	$956.80