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	$66.90	9.529%	$73.2749	$73.27	$73.25	$73.30
Purchase #2	$28.89	6.240%	$30.6927	$30.69	$30.70	$30.70
Purchase #3	$98.91	3.544%	$102.4154	$102.42	$102.40	$102.40
Purchase #4	$244.42	9.673%	$268.0627	$268.06	$268.05	$268.10
Purchase #5	$64.25	12.818%	$72.4856	$72.49	$72.50	$72.50
Purchase #6	$120.55	5.662%	$127.3755	$127.38	$127.40	$127.40
Purchase #7	$215.48	8.237%	$233.2291	$233.23	$233.25	$233.20
7 purchase totals =	$839.40		$907.5359	$907.54	$907.55	$907.60