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	$98.86	10.486%	$109.2265	$109.23	$109.25	$109.20
Purchase #2	$53.70	3.431%	$55.5424	$55.54	$55.55	$55.50
Purchase #3	$91.45	9.220%	$99.8817	$99.88	$99.90	$99.90
Purchase #4	$122.90	3.391%	$127.0675	$127.07	$127.05	$127.10
Purchase #5	$63.61	8.135%	$68.7847	$68.78	$68.80	$68.80
Purchase #6	$232.86	7.730%	$250.8601	$250.86	$250.85	$250.90
Purchase #7	$152.76	12.279%	$171.5174	$171.52	$171.50	$171.50
7 purchase totals =	$816.14		$882.8803	$882.88	$882.90	$882.90