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	$57.27	8.835%	$62.3298	$62.33	$62.35	$62.30
Purchase #2	$185.99	7.670%	$200.2554	$200.26	$200.25	$200.30
Purchase #3	$125.64	7.604%	$135.1937	$135.19	$135.20	$135.20
Purchase #4	$97.85	3.111%	$100.8941	$100.89	$100.90	$100.90
Purchase #5	$68.31	4.717%	$71.5322	$71.53	$71.55	$71.50
Purchase #6	$219.41	13.780%	$249.6447	$249.64	$249.65	$249.60
Purchase #7	$54.85	4.608%	$57.3775	$57.38	$57.40	$57.40
7 purchase totals =	$809.32		$877.2274	$877.22	$877.30	$877.20