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	$129.64	10.163%	$142.8153	$142.82	$142.80	$142.80
Purchase #2	$168.40	10.646%	$186.3279	$186.33	$186.35	$186.30
Purchase #3	$196.53	6.528%	$209.3595	$209.36	$209.35	$209.40
Purchase #4	$225.42	7.740%	$242.8675	$242.87	$242.85	$242.90
Purchase #5	$153.51	9.216%	$167.6575	$167.66	$167.65	$167.70
Purchase #6	$12.63	8.676%	$13.7258	$13.73	$13.75	$13.70
Purchase #7	$62.29	8.665%	$67.6874	$67.69	$67.70	$67.70
7 purchase totals =	$948.42		$1,030.4409	$1,030.46	$1,030.45	$1,030.50