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	$174.67	7.259%	$187.3493	$187.35	$187.35	$187.30
Purchase #2	$150.84	4.661%	$157.8707	$157.87	$157.85	$157.90
Purchase #3	$213.31	10.114%	$234.8842	$234.88	$234.90	$234.90
Purchase #4	$165.52	13.815%	$188.3866	$188.39	$188.40	$188.40
Purchase #5	$82.36	9.106%	$89.8597	$89.86	$89.85	$89.90
Purchase #6	$136.66	4.466%	$142.7632	$142.76	$142.75	$142.80
Purchase #7	$91.79	11.747%	$102.5726	$102.57	$102.55	$102.60
7 purchase totals =	$1,015.15		$1,103.6863	$1,103.68	$1,103.65	$1,103.80