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	$106.95	11.147%	$118.8717	$118.87	$118.85	$118.90
Purchase #2	$96.63	3.443%	$99.957	$99.96	$99.95	$100.00
Purchase #3	$174.29	4.368%	$181.903	$181.90	$181.90	$181.90
Purchase #4	$152.88	4.358%	$159.5425	$159.54	$159.55	$159.50
Purchase #5	$67.80	9.761%	$74.418	$74.42	$74.40	$74.40
Purchase #6	$13.71	4.217%	$14.2882	$14.29	$14.30	$14.30
Purchase #7	$137.35	5.240%	$144.5471	$144.55	$144.55	$144.50
7 purchase totals =	$749.61		$793.5275	$793.53	$793.50	$793.50