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	$160.87	6.221%	$170.8777	$170.88	$170.90	$170.90
Purchase #2	$142.82	6.374%	$151.9233	$151.92	$151.90	$151.90
Purchase #3	$84.63	7.193%	$90.7174	$90.72	$90.70	$90.70
Purchase #4	$190.40	3.412%	$196.8964	$196.90	$196.90	$196.90
Purchase #5	$38.98	7.154%	$41.7686	$41.77	$41.75	$41.80
Purchase #6	$221.36	3.700%	$229.5503	$229.55	$229.55	$229.60
Purchase #7	$134.86	9.518%	$147.696	$147.70	$147.70	$147.70
7 purchase totals =	$973.92		$1,029.4297	$1,029.44	$1,029.40	$1,029.50