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	$37.70	11.163%	$41.9085	$41.91	$41.90	$41.90
Purchase #2	$91.61	9.223%	$100.0592	$100.06	$100.05	$100.10
Purchase #3	$236.69	3.515%	$245.0097	$245.01	$245.00	$245.00
Purchase #4	$204.78	11.269%	$227.8567	$227.86	$227.85	$227.90
Purchase #5	$151.33	10.292%	$166.9049	$166.90	$166.90	$166.90
Purchase #6	$179.99	9.334%	$196.7903	$196.79	$196.80	$196.80
Purchase #7	$92.43	5.653%	$97.6551	$97.66	$97.65	$97.70
7 purchase totals =	$994.53		$1,076.1844	$1,076.19	$1,076.15	$1,076.30