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	$159.61	7.330%	$171.3094	$171.31	$171.30	$171.30
Purchase #2	$174.88	5.159%	$183.9021	$183.90	$183.90	$183.90
Purchase #3	$101.53	13.498%	$115.2345	$115.23	$115.25	$115.20
Purchase #4	$142.88	11.576%	$159.4198	$159.42	$159.40	$159.40
Purchase #5	$153.91	10.109%	$169.4688	$169.47	$169.45	$169.50
Purchase #6	$158.96	9.753%	$174.4634	$174.46	$174.45	$174.50
Purchase #7	$36.65	3.125%	$37.7953	$37.80	$37.80	$37.80
7 purchase totals =	$928.42		$1,011.5933	$1,011.59	$1,011.55	$1,011.60