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	$145.80	4.223%	$151.9571	$151.96	$151.95	$152.00
Purchase #2	$51.60	5.365%	$54.3683	$54.37	$54.35	$54.40
Purchase #3	$204.94	6.758%	$218.7898	$218.79	$218.80	$218.80
Purchase #4	$214.91	8.424%	$233.014	$233.01	$233.00	$233.00
Purchase #5	$183.56	7.154%	$196.6919	$196.69	$196.70	$196.70
Purchase #6	$37.91	12.589%	$42.6825	$42.68	$42.70	$42.70
Purchase #7	$51.44	3.148%	$53.0593	$53.06	$53.05	$53.10
7 purchase totals =	$890.16		$950.5629	$950.56	$950.55	$950.70