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	$181.87	5.342%	$191.5855	$191.59	$191.60	$191.60
Purchase #2	$27.40	11.408%	$30.5258	$30.53	$30.55	$30.50
Purchase #3	$78.97	5.740%	$83.5029	$83.50	$83.50	$83.50
Purchase #4	$235.55	11.442%	$262.5016	$262.50	$262.50	$262.50
Purchase #5	$151.28	4.658%	$158.3266	$158.33	$158.35	$158.30
Purchase #6	$94.43	11.725%	$105.5019	$105.50	$105.50	$105.50
Purchase #7	$156.79	6.618%	$167.1664	$167.17	$167.15	$167.20
7 purchase totals =	$926.29		$999.1107	$999.12	$999.15	$999.10