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	$86.86	5.399%	$91.5496	$91.55	$91.55	$91.50
Purchase #2	$127.69	4.542%	$133.4897	$133.49	$133.50	$133.50
Purchase #3	$18.50	4.334%	$19.3018	$19.30	$19.30	$19.30
Purchase #4	$23.57	8.449%	$25.5614	$25.56	$25.55	$25.60
Purchase #5	$69.40	13.690%	$78.9009	$78.90	$78.90	$78.90
Purchase #6	$22.83	12.250%	$25.6267	$25.63	$25.65	$25.60
Purchase #7	$97.27	5.270%	$102.3961	$102.40	$102.40	$102.40
7 purchase totals =	$446.12		$476.8262	$476.83	$476.85	$476.80