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	$165.47	12.622%	$186.3556	$186.36	$186.35	$186.40
Purchase #2	$185.54	4.731%	$194.3179	$194.32	$194.30	$194.30
Purchase #3	$52.33	4.198%	$54.5268	$54.53	$54.55	$54.50
Purchase #4	$241.97	3.274%	$249.8921	$249.89	$249.90	$249.90
Purchase #5	$29.84	12.343%	$33.5232	$33.52	$33.50	$33.50
Purchase #6	$183.62	4.449%	$191.7893	$191.79	$191.80	$191.80
Purchase #7	$164.45	10.158%	$181.1548	$181.15	$181.15	$181.20
7 purchase totals =	$1,023.22		$1,091.5597	$1,091.56	$1,091.55	$1,091.60