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	$51.93	3.202%	$53.5928	$53.59	$53.60	$53.60
Purchase #2	$136.27	4.431%	$142.3081	$142.31	$142.30	$142.30
Purchase #3	$153.83	3.628%	$159.411	$159.41	$159.40	$159.40
Purchase #4	$174.36	4.319%	$181.8906	$181.89	$181.90	$181.90
Purchase #5	$157.96	5.430%	$166.5372	$166.54	$166.55	$166.50
Purchase #6	$70.87	9.723%	$77.7607	$77.76	$77.75	$77.80
Purchase #7	$231.74	7.779%	$249.7671	$249.77	$249.75	$249.80
7 purchase totals =	$976.96		$1,031.2675	$1,031.27	$1,031.25	$1,031.30