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	$165.63	8.628%	$179.9206	$179.92	$179.90	$179.90
Purchase #2	$161.30	13.144%	$182.5013	$182.50	$182.50	$182.50
Purchase #3	$181.60	6.315%	$193.068	$193.07	$193.05	$193.10
Purchase #4	$51.86	11.512%	$57.8301	$57.83	$57.85	$57.80
Purchase #5	$173.93	13.121%	$196.7514	$196.75	$196.75	$196.80
Purchase #6	$52.62	7.232%	$56.4255	$56.43	$56.45	$56.40
Purchase #7	$198.84	6.145%	$211.0587	$211.06	$211.05	$211.10
7 purchase totals =	$985.78		$1,077.5556	$1,077.56	$1,077.55	$1,077.60