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	$96.99	6.300%	$103.1004	$103.10	$103.10	$103.10
Purchase #2	$180.83	6.399%	$192.4013	$192.40	$192.40	$192.40
Purchase #3	$48.87	4.385%	$51.0129	$51.01	$51.00	$51.00
Purchase #4	$94.33	5.331%	$99.3587	$99.36	$99.35	$99.40
Purchase #5	$169.62	7.214%	$181.8564	$181.86	$181.85	$181.90
Purchase #6	$56.70	8.347%	$61.4327	$61.43	$61.45	$61.40
Purchase #7	$121.83	4.528%	$127.3465	$127.35	$127.35	$127.30
7 purchase totals =	$769.17		$816.5089	$816.51	$816.50	$816.50