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	$179.60	5.374%	$189.2517	$189.25	$189.25	$189.30
Purchase #2	$151.39	13.276%	$171.4885	$171.49	$171.50	$171.50
Purchase #3	$61.33	6.494%	$65.3128	$65.31	$65.30	$65.30
Purchase #4	$205.38	8.835%	$223.5253	$223.53	$223.55	$223.50
Purchase #5	$114.42	6.313%	$121.6433	$121.64	$121.65	$121.60
Purchase #6	$112.73	10.562%	$124.6365	$124.64	$124.65	$124.60
Purchase #7	$159.95	7.465%	$171.8903	$171.89	$171.90	$171.90
7 purchase totals =	$984.80		$1,067.7484	$1,067.75	$1,067.80	$1,067.70