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	$176.72	4.722%	$185.0647	$185.06	$185.05	$185.10
Purchase #2	$123.93	12.596%	$139.5402	$139.54	$139.55	$139.50
Purchase #3	$147.90	6.804%	$157.9631	$157.96	$157.95	$158.00
Purchase #4	$41.67	6.659%	$44.4448	$44.44	$44.45	$44.40
Purchase #5	$143.86	9.854%	$158.036	$158.04	$158.05	$158.00
Purchase #6	$130.96	11.375%	$145.8567	$145.86	$145.85	$145.90
Purchase #7	$142.57	9.710%	$156.4135	$156.41	$156.40	$156.40
7 purchase totals =	$907.61		$987.3190	$987.31	$987.30	$987.30