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	$152.39	12.254%	$171.0639	$171.06	$171.05	$171.10
Purchase #2	$105.64	3.223%	$109.0448	$109.04	$109.05	$109.00
Purchase #3	$27.55	12.139%	$30.8943	$30.89	$30.90	$30.90
Purchase #4	$209.59	11.386%	$233.4539	$233.45	$233.45	$233.50
Purchase #5	$175.81	10.577%	$194.4054	$194.41	$194.40	$194.40
Purchase #6	$229.83	10.484%	$253.9254	$253.93	$253.95	$253.90
Purchase #7	$196.55	6.758%	$209.8328	$209.83	$209.85	$209.80
7 purchase totals =	$1,097.36		$1,202.6205	$1,202.61	$1,202.65	$1,202.60