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	$127.70	4.478%	$133.4184	$133.42	$133.40	$133.40
Purchase #2	$106.76	11.777%	$119.3331	$119.33	$119.35	$119.30
Purchase #3	$178.77	9.690%	$196.0928	$196.09	$196.10	$196.10
Purchase #4	$171.51	13.335%	$194.3809	$194.38	$194.40	$194.40
Purchase #5	$108.34	6.113%	$114.9628	$114.96	$114.95	$115.00
Purchase #6	$159.92	12.599%	$180.0683	$180.07	$180.05	$180.10
Purchase #7	$77.86	9.342%	$85.1337	$85.13	$85.15	$85.10
7 purchase totals =	$930.86		$1,023.3900	$1,023.38	$1,023.40	$1,023.40