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	$185.44	5.714%	$196.036	$196.04	$196.05	$196.00
Purchase #2	$175.74	13.102%	$198.7655	$198.77	$198.75	$198.80
Purchase #3	$236.95	11.524%	$264.2561	$264.26	$264.25	$264.30
Purchase #4	$190.92	5.526%	$201.4702	$201.47	$201.45	$201.50
Purchase #5	$92.99	13.215%	$105.2786	$105.28	$105.30	$105.30
Purchase #6	$166.69	13.544%	$189.2665	$189.27	$189.25	$189.30
Purchase #7	$147.70	7.222%	$158.3669	$158.37	$158.35	$158.40
7 purchase totals =	$1,196.43		$1,313.4398	$1,313.46	$1,313.40	$1,313.60