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	$72.52	13.404%	$82.2406	$82.24	$82.25	$82.20
Purchase #2	$149.34	10.177%	$164.5383	$164.54	$164.55	$164.50
Purchase #3	$190.42	11.395%	$212.1184	$212.12	$212.10	$212.10
Purchase #4	$103.69	8.330%	$112.3274	$112.33	$112.35	$112.30
Purchase #5	$245.91	6.172%	$261.0876	$261.09	$261.10	$261.10
Purchase #6	$118.84	7.251%	$127.4571	$127.46	$127.45	$127.50
Purchase #7	$82.86	12.575%	$93.2796	$93.28	$93.30	$93.30
7 purchase totals =	$963.58		$1,053.0490	$1,053.06	$1,053.10	$1,053.00