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	$39.69	3.195%	$40.9581	$40.96	$40.95	$41.00
Purchase #2	$53.90	9.870%	$59.2199	$59.22	$59.20	$59.20
Purchase #3	$25.63	5.582%	$27.0607	$27.06	$27.05	$27.10
Purchase #4	$90.85	5.803%	$96.122	$96.12	$96.10	$96.10
Purchase #5	$135.32	6.713%	$144.404	$144.40	$144.40	$144.40
Purchase #6	$13.73	4.389%	$14.3326	$14.33	$14.35	$14.30
Purchase #7	$19.94	7.472%	$21.4299	$21.43	$21.45	$21.40
7 purchase totals =	$379.06		$403.5272	$403.52	$403.50	$403.50