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	$231.68	5.799%	$245.1151	$245.12	$245.10	$245.10
Purchase #2	$24.31	4.148%	$25.3184	$25.32	$25.30	$25.30
Purchase #3	$34.54	12.589%	$38.8882	$38.89	$38.90	$38.90
Purchase #4	$180.76	8.786%	$196.6416	$196.64	$196.65	$196.60
Purchase #5	$114.96	3.599%	$119.0974	$119.10	$119.10	$119.10
Purchase #6	$79.99	4.144%	$83.3048	$83.30	$83.30	$83.30
Purchase #7	$158.45	5.566%	$167.2693	$167.27	$167.25	$167.30
7 purchase totals =	$824.69		$875.6348	$875.64	$875.60	$875.60