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	$183.84	3.572%	$190.4068	$190.41	$190.40	$190.40
Purchase #2	$39.34	7.869%	$42.4357	$42.44	$42.45	$42.40
Purchase #3	$75.44	5.851%	$79.854	$79.85	$79.85	$79.90
Purchase #4	$240.71	11.865%	$269.2702	$269.27	$269.25	$269.30
Purchase #5	$112.48	13.192%	$127.3184	$127.32	$127.30	$127.30
Purchase #6	$40.57	8.216%	$43.9032	$43.90	$43.90	$43.90
Purchase #7	$188.92	6.762%	$201.6948	$201.69	$201.70	$201.70
7 purchase totals =	$881.30		$954.8831	$954.88	$954.85	$954.90