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	$144.96	13.498%	$164.5267	$164.53	$164.55	$164.50
Purchase #2	$156.84	3.740%	$162.7058	$162.71	$162.70	$162.70
Purchase #3	$85.65	5.554%	$90.407	$90.41	$90.40	$90.40
Purchase #4	$239.27	3.730%	$248.1948	$248.19	$248.20	$248.20
Purchase #5	$165.80	3.228%	$171.152	$171.15	$171.15	$171.20
Purchase #6	$196.33	13.833%	$223.4883	$223.49	$223.50	$223.50
Purchase #7	$236.43	13.576%	$268.5277	$268.53	$268.55	$268.50
7 purchase totals =	$1,225.28		$1,329.0023	$1,329.01	$1,329.05	$1,329.00