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	$101.90	10.290%	$112.3855	$112.39	$112.40	$112.40
Purchase #2	$30.51	4.569%	$31.904	$31.90	$31.90	$31.90
Purchase #3	$6.96	12.614%	$7.8379	$7.84	$7.85	$7.80
Purchase #4	$102.39	11.655%	$114.3236	$114.32	$114.30	$114.30
Purchase #5	$224.25	5.188%	$235.8841	$235.88	$235.90	$235.90
Purchase #6	$224.25	11.179%	$249.3189	$249.32	$249.30	$249.30
Purchase #7	$240.95	9.860%	$264.7077	$264.71	$264.70	$264.70
7 purchase totals =	$931.21		$1,016.3617	$1,016.36	$1,016.35	$1,016.30