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	$176.33	5.332%	$185.7319	$185.73	$185.75	$185.70
Purchase #2	$112.31	13.308%	$127.2562	$127.26	$127.25	$127.30
Purchase #3	$191.53	7.427%	$205.7549	$205.75	$205.75	$205.80
Purchase #4	$137.89	13.140%	$156.0087	$156.01	$156.00	$156.00
Purchase #5	$38.37	4.571%	$40.1239	$40.12	$40.10	$40.10
Purchase #6	$68.63	5.173%	$72.1802	$72.18	$72.20	$72.20
Purchase #7	$120.65	10.571%	$133.4039	$133.40	$133.40	$133.40
7 purchase totals =	$845.71		$920.4597	$920.45	$920.45	$920.50