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	$124.31	7.502%	$133.6357	$133.64	$133.65	$133.60
Purchase #2	$108.96	13.104%	$123.2381	$123.24	$123.25	$123.20
Purchase #3	$92.38	4.568%	$96.5999	$96.60	$96.60	$96.60
Purchase #4	$203.87	5.668%	$215.4254	$215.43	$215.45	$215.40
Purchase #5	$240.29	13.386%	$272.4552	$272.46	$272.45	$272.50
Purchase #6	$157.27	4.552%	$164.4289	$164.43	$164.45	$164.40
Purchase #7	$95.41	13.809%	$108.5852	$108.59	$108.60	$108.60
7 purchase totals =	$1,022.49		$1,114.3684	$1,114.39	$1,114.45	$1,114.30