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	$249.38	13.372%	$282.7271	$282.73	$282.75	$282.70
Purchase #2	$54.72	5.424%	$57.688	$57.69	$57.70	$57.70
Purchase #3	$35.39	8.440%	$38.3769	$38.38	$38.40	$38.40
Purchase #4	$200.41	4.442%	$209.3122	$209.31	$209.30	$209.30
Purchase #5	$72.34	5.765%	$76.5104	$76.51	$76.50	$76.50
Purchase #6	$59.78	8.839%	$65.064	$65.06	$65.05	$65.10
Purchase #7	$127.39	13.844%	$145.0259	$145.03	$145.05	$145.00
7 purchase totals =	$799.41		$874.7045	$874.71	$874.75	$874.70