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	$84.46	6.477%	$89.9305	$89.93	$89.95	$89.90
Purchase #2	$220.89	10.776%	$244.6931	$244.69	$244.70	$244.70
Purchase #3	$47.32	3.322%	$48.892	$48.89	$48.90	$48.90
Purchase #4	$249.31	11.765%	$278.6413	$278.64	$278.65	$278.60
Purchase #5	$98.56	13.841%	$112.2017	$112.20	$112.20	$112.20
Purchase #6	$57.59	6.459%	$61.3097	$61.31	$61.30	$61.30
Purchase #7	$107.39	6.764%	$114.6539	$114.65	$114.65	$114.70
7 purchase totals =	$865.52		$950.3222	$950.31	$950.35	$950.30