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	$92.30	12.180%	$103.5421	$103.54	$103.55	$103.50
Purchase #2	$107.37	6.684%	$114.5466	$114.55	$114.55	$114.50
Purchase #3	$156.90	9.394%	$171.6392	$171.64	$171.65	$171.60
Purchase #4	$191.39	4.541%	$200.081	$200.08	$200.10	$200.10
Purchase #5	$178.68	8.769%	$194.3484	$194.35	$194.35	$194.30
Purchase #6	$81.40	4.852%	$85.3495	$85.35	$85.35	$85.30
Purchase #7	$43.31	6.466%	$46.1104	$46.11	$46.10	$46.10
7 purchase totals =	$851.35		$915.6172	$915.62	$915.65	$915.40