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	$92.71	9.270%	$101.3042	$101.30	$101.30	$101.30
Purchase #2	$243.52	12.468%	$273.8821	$273.88	$273.90	$273.90
Purchase #3	$147.76	12.662%	$166.4694	$166.47	$166.45	$166.50
Purchase #4	$103.27	9.181%	$112.7512	$112.75	$112.75	$112.80
Purchase #5	$124.87	4.495%	$130.4829	$130.48	$130.50	$130.50
Purchase #6	$200.46	4.154%	$208.7871	$208.79	$208.80	$208.80
Purchase #7	$134.67	9.405%	$147.3357	$147.34	$147.35	$147.30
7 purchase totals =	$1,047.26		$1,141.0126	$1,141.01	$1,141.05	$1,141.10